The issue of using citation based indicators in the evaluation of science is widely discussed. Only recently did bibliometric indicators become one out of many means for the allocation of financial resources for scientific research at Swedish universities. The purpose of this thesis is to discuss the issue of using citations when evaluating science. The author studied the issue from the perspective of citers’ motives. Previous studies indicate differences in motivations for citing between separate research fields. The thesis will focus on the field of cardiology. A qualitative interview study with cardiology scientists is balanced against existing literature in the field of citers’ motives and evaluated in a theoretical framework based on normative and social constructivist theories. Results indicate multiple motives for citing. Normative reasons were generally more common but social constructivist motives were also observed. This outcome supports the notion that there exists no unifying citation theory. The use of citations within science evaluation is moderately supported, depending on the definition of the term science evaluation. The interview study implies that references are mainly chosen based on quality and relevance but instances of less preferable elements as persuasion, favouring national references and randomness of reference selection does also occur. This thesis is an incentive to continue studying citers’ motives in relation to citation oriented science evaluation within different fields of scholarship. A thorough quantitative study would either validate or question the use of citations within research evaluation on a more general level.