Campylobacter jejuni is an important cause of food-borne gastroenteritis and enteritis in humans in many developed countries. Several C. jejuni virulence determinants have been identified. The purpose of our experiments was to determine the prevalence of virulence and toxin genes cadF, flaA, cdtA, cdtB, cdtC, cdtABC, virB11 among 102 C. jejuni isolates isolated in Poland between 2003 and 2005 from humans with diarrhea. The PCR analysis of the strains revealed the presence of the flaA and the cadF genes among all C. jejuni isolates. Detection rates for the cdtA, cdtB, cdtC and cdtABC cluster genes were 98, 96, 92 and 88% respectively. The virB11 gene was found in only 3% of the isolates. The high prevalence of cadF, flaA and cdt genes demonstrated that these genes may play an important role in C. jejuni virulence. Further research is necessary to clarify the importance of the virB11 gene in the pathogenesis of infections with C. jejuni strains in humans.