Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Successful merger and acquisitions (M & A) from a financial perspective increases shareholder value. This paper examines the effect of corporate mergers and acquisitions (M & A) on shareholder value. A discussion on shareholder value follows with reasons why companies choose M & A as a growth strategy. The type of M & A strategy affects the value it creates. A literature review of M & A activity during the five periods in the twentieth century, referred to as merger waves, provides an understanding of the conditions which precipitate M & A activity. However, failure of companies that engage in M & A activity has not resulted in a decline in the popularity of M & A. This study identifies and subsequently analyses data (profitability ratios) on 34 upstream oil and gas companies that have engaged in M & A activity. Profitability ratios indicate the financial performance of a company and ultimately shareholder value. In order to obtain the best possible insights into the behaviour of the identified variables and their impact on shareholder value, the specific variables are empirically tested over different time periods through the application of two statistical tests performed on the data. The empirical analysis is based on a total of 324 observations gathered by Evaluate Energy for global oil and gas companies and covers the period 1995 to 2005. The results of the different testing methods, although subject to certain limitations, give reason to believe that the M & A leads to an erosion of shareholder value. Hence the appropriate reasons for embarking on an M & A strategy and the comprehensive pre-acquisition evaluation thereof, is tantamount to M & A success. / AFRIKAANSE OPSOMMING: Vanuit ‘n finansiële oogpunt kan suksesvolle samesmeltings en aanskaffings (S & A) aandeelhouers-waarde verhoog en hierdie werkstuk ontleed die effek wat korporatiewe S & A’s op aandeelhouers-waarde het. ‘n Bespreking oor aandeelhouers-waarde volg en verskaf redes waarom maatskappye S & A’s as ‘n groeistrategie verkies en hoe die tipe S & A strategie wat gevolg word die waarde wat dit skep affekteer. Gedurende die 20ste eeu was daar vyf tydperke waarin S & A aktiwiteite hoog was, die sogenaamde “merger waves” en ‘n ontleding van literatuur gedurende hierdie tydperke verskaf ‘n begrip van die omstandighede wat aanleiding gee tot S & A aktiwiteite. Alhoewel sommige S & A’s onsuksesvol is, bly dit ‘n populêre keuse by maatskappye om aandeelhouers-waarde te probeer verhoog. Hierdie studie identifiseer en analiseer data (winsgewendheids-verhoudings) van 34 “upstream” olie- en gasmaatskappye wat een of ander tyd in ‘n S & A betrokke was. Winsgewendheids-verhoudings dui op die finansiële prestasie van maatskappye en uiteindelik op aandeelhouers-waarde. Ten einde die beste insae in die optrede van die geidentifiseerde veranderlikes en hul impak op aandeelhouers-waarde te kry, is die spesifieke veranderlikes numeries getoets oor verskillende tydperke deur middel van twee statistiese modelle. Die numeriese analises is gebaseer op 324 waarnemings deur Evaluate Energy op internasionale olie- en gasmaatskappye tussen 1995 en 2005. Die uitslae van die verskillende metodes van toets, ingesluit sekere beperkings, dui daarop dat S & A’s oor die algemeen lei tot ‘n vermindering in aandeelhouers-waarde en daarom is dit van kardinale belang om ‘n beproefde S & A strategie te ontwikkel voordat ‘n S & A aangepak word.