This paper considers basic causes of corruption in Serbia, on the one side, and changes that occurred between the two researches (2001-2006), on the other side. In 2001 research, the entrepreneurs main causes of corruption see in: small wages of clerks working in public sector (59%), moral crisis in period of transition (43%), inadequate legislation (43%), aspirations of people in power to get rich quickly (39%), involving of personal interest in public job (26%), lack of strong administrative control (22%), specific character of our culture (21%) and problems occurred as a consequence of communistic past (17%). Five years later, first place, as a cause of corruption, takes moral crisis (49), ambitions of people in power to get rich quickly - irresponsible politic elite (46%), small wages of clerks working in public sector (44%), inadequate legislation (39%), involving of personal interest in public job(31%) and specific character of our culture (13%). Public opinion survey shows somewhat different results - moral crisis (52%), general poverty (51%), absence of rule of the law (39,6%), inefficient judicial system (25,9%), political system (20,9%), legislation (19%), war and sanctions (15,5%), human nature (13,6%), small wages of clerks working in public sector (11%) etc. Considering the results of these researches, key causes of corruption can be found in two groups of facts: inner ones (absence of rule of the law, moral crisis and moral confusion, irresponsible political elite, lack of political will and transition) and outer ones (break-up of Yugoslavia, war in the region and sanctions, helping the Kosovo crisis by West, bombarding and various and constant pressures from "international community").