Family, twin and adoption studies have shown that genetic factors have an important role in the etiology of bipolar affective disorder. In this study, 30 bipolar cases whose diagnoses were determined by the Pychiatry department and 15 healthy individuals were compared with respect to fragile sites. APC, BrdU, FUdR and MTX were used as fragile site inducers. No significant difference was found between the rates of fragile sites observed in the patient and control groups. The fragile sites that were observed most freguently in the patient group were 1q21, 1q44, 2q32, 6p22, 6p26 and 10q25. No fragile site accumulation could be found on chromosomes 11 and X, where gene locuses are likely to exist. Nor was any cytogenetic association found between FXS and bipolar disorder. It was determined that age and sex do not influence the frequency of fragile sites.