Samhällsvetenskapliga portalfigurer som Durkheim, Marx och Weber har medverkat i diskussionen om aktör och struktur. Diskussionen om intentioner; agerande och samhällsstrukturer pågår fortfarande. Om de samhällsvetenskapliga fenomenen utgår från individen – aktören – och/eller dess omgivning - strukturen - är en evig fråga. Denna avhandling är ett bidrag till den moderna diskussionen om aktör och struktur. Syftet är att analysera problemkomplexet aktör-struktur. Många tidigare studier i genren är abstrakta och generella. I detta arbete studeras också samhällsforskares tillämpning. Efter analyser av den aktörsteoretiska ansatsen (statsvetaren Axel Hadenius' forskning, den strukturteoretiska ansatsen (sociologen Bruce Mayhews forskning), samt a ansatsen (statsvetaren Bo Rothsteins forskning), samt redovisas ett preciserat förhållningssätt till problemkomplexet. Studiens utgångspunkt är att både den ensidiga aktörsteoretiska ansatsen och den ensidiga strukturteoretiska ansatsen kommer att uppvisa brister. De respektive ensidiga ansatserna antas inte brista främst på grund av sin ensidighet, vilket flera företrädare för den aktör-strukturteoretiska ansatsen hävdar. Utifrån avhandlingens vägledande analysram förväntas de respektive ensidiga ansatsernas filosofier, teorier och förklaringar brista på så sätt att företrädarnas programförklaringar inte stämmer överens med företrädarnas tillämpningar. Därmed uppfyller de ensidiga ansatsernas företrädare inte det grundläggande kravet på vetenskaplig klarhet. Av analysen framgår att det i den aktörsteoretiska ansatsens tillämpning också återfinns strukturfaktorer av ett slag som ansatsens företrädare programmatiskt vill utesluta. I den tillämpade strukturteoretiska ansatsen återfinns aktörsfaktorer. Också den aktör-strukturteoretiska ansats som analyseras uppvisar brister i överensstämmelse mellan programförklaring och tillämpning. Resultaten tas till intäkt för att överge både den individualism som den aktörsteoretiska ansatsen vilar på och den strukturalism sätts i detta arbete den filosofiska antagande att den samhälleliga verkligheten innehåller både aktör och struktur, Antagandet om samhällets tvåsidighet utgör en viktig grund för den preciserande aktör-strukturteoretiska ansats som är studiens övergripande slutsats. / This thesis is a contribution to the age-old discussion in the social sciences about actor and structure. From the outset it is argued that the question of actor and structure constitutes a complexity of problems which contains philosophical, theoretical and explanatory elements. Different ways of comprehending the complexity of problems constitute a watershed between research approaches. The three main approaches are the actor theoretical approach, the structural theoretical approach and 1he actor-structural theoretical approach. The purpose of this study is to analyse these three approaches and thereby present a fruitful approach to the complexity of problems. The author adopts the combined actor-structural theoretical approach from the start, but not in an uncritical and self-evident manner. This study is based on two lines of argumentation. Firstly, it is stipulated that a social scientist's research programme on actor and structure should be consistent With the researcher's application. Secondly, it is stipulated that social reality consists of both actor and s1ructure, and that actor and  structure do not mean the same thing. The author's suggestion is that this idea about the two-sidedness of soc iety is a prerequisite for interna! consistency. Hence, traces of both actor and structure should a lso be found in the applications of the two one-sided approaches. In order to discern the one-sided actor theoretical approach, three ideas are stipulated as philosophy, theory and explanation in a specified ideal type: methodological individualism, instrumental rationality and intentional explanation. These ideas are present in the research programme of the chosen representative of the actor theoretical approach, the Swedish political scientist Axel Hadenius. It is found that Hadenius' application does not correspond with his research programme. In his application. factors occur that are not totally reducible to facts aboul separale or aggregated individuals. In order to discern the one-sided sructural theoretical approach, three ideas are stipulated as philosophy. theory and explanation in a specified ideal type: structuralism, theoretical relations between structures and nomothetical-deductive explanations with structures. These ideas are present in the research programme of the chosen representative of the structural theoretical approach, the American sociologi st Bruce Mayhew. It is found that Mayhew's application does not correspond with his research programme. In his application, fac1s about separate or aggregated individuals occur. The three ideas behind the ideal type actor-structural theoretical approach are two-sided level realism, theoretical actor-structural relations and actor-structural explanation. These ideas are present in the research programme of the chosen representative of the actor-structural theoretical approach, the Swedish political scientist Bo Rothstein, even if there are also traces leading off in other directions. Finally, the testing of the occurrence of the preliminary actor-structural approach in the three research approaches is combined with the elabora1ion of philosophy, theory and explana1ion in the specified actorstructural theoretical approach. The latter approach constitutes the author's stand on the complexity of problems of actor and structure. The philosophy in the specified approach, two-sided leve! realism, is allegedly composed of three closely related ideas: actual closeness between actor and structure, situational irreducibility, and the relational concept of social structure. The idea of the theoretical relation between actor and structure is allegedly composed of three closely related ideas: empirical openness, analytical dualism and generative mechanisms. All are, in tum, closely related to the three ideas of the two-sided leve! realism, as well as to the idea of actor-structural explanation. The specified approach lays the foundations for clarity in terms of internat logical congruence between research programme and application.