Spontaneous chromosome aberrations (CAs) and induced fragile sites (FSs) were analysed in 12 untreated adult coeliac disease (CD) patients and 8 healthy controls. Blood lymphocytes from each individual were cultured for 72 h at 37 degrees C in F-10 medium with 5% fetal calf serum and 0.1 ml phytohemagglutinine. FSs were induced by FudR (10 micrograms/ml, 24 h before harvesting) and caffeine (2.2 mM. 6 h before harvest). Spontaneous CAs and FSs were analysed on 30-50 Giemsa-stained and G-banded metaphases. The mean frequencies of spontaneous CAs (abnormal cells, gaps/cell and breaks/cell) of CD patients (0.24 +/- 0.02, 0.21 +/- 0.02 and 0.13 +/- 0.02, respectively) were significantly higher than those of controls (0.04 +/- 0.01, 0.02 +/- 0.01 and 0.02 +/- 0.01, respectively) (p < 0.001). Fourteen spontaneous CAs and 5 FSs specific for CD patients presented a strong coincidence (70%) with bands involved in T- and B-cell malignant lymphoma rearrangements. These findings suggest that CD has chromosome instability affecting specific points that could be related to the high prevalence of malignancies in this disorder.