Cystic echinococcosis (CE) due to Echinococcus granulosus is one of the most important helminthic diseases in Turkey where it constitutes a public health and economic problems. Its mean annual incidence in humans is 4.4/100 000 and the prevalence of the tapeworm agent in domestic animals ranges from 11.2 to 50.7%. Since 1980s, albendazole has been used for treatment of the disease, and this benzimidazole drug has been considered to be of relatively low toxicity. However, prolonged albendazole therapy of CE became to be a common practice, and data on possible genotoxic effects of the medication in humans are lacking. This study has concerned 17 women and 11 men, in total 28 patients with liver cystic hydatid complaints, who were administered albendazole ( 15 mg/kg) preoperatively ( 2 weeks) and postoperatively ( 6 months). Genotoxic effects of albendazole were searched using Sister Chromatid Exchange ( SCE), mitotic index (MI) and chromosomal aberations (CAs) methods, comparing lymphocyte chromosomes of treated patients and a control group of healthy individuals. The results indicated a significant increase of SCE frequencies and decrease of MI in the treated group ( p < 0.001). Regarding CAs, any difference between the groups was not determined.