OBJECTIVE To study the prevalence of hepatitis B and C viruses in patients with glomerulonephritis (Gn). Material and methods. This was a retrospective study of 89 patients (36 females, 53 males) diagnosed with Gn. Infection with hepatitis B and C was studied by means of serological methods; if patients presented hepatitis C antibodies, the presence of viral RNA in serum was detected by means of quantitative polymerase chain reaction. The control group comprised 59,546 first-time blood donors. RESULTS None of the patients were positive for hepatitis B surface antigen (HBsAg). In the control group there were 168 HBsAg positives. The prevalence of HBsAg in the control group (0.28%) was not significantly different (p = 0.614) from that in the patient group. Four patients with Gn were positive for hepatitis C virus (HCV) antibodies, and in three of these RNA HCV was also positive. The histological diagnoses in the four cases with HCV antibodies were: focal and segmental glomerulosclerosis; crescentic IgA nephropathy; diffuse proliferative Gn; and membranous Gn. The first three patients also presented other pathologies potentially linked to Gn, namely left renal agenesis, heavy alcohol intake/chronic liver disease and HIV seropositivity, respectively. Only the patient with membranous Gn, in whom other causes were disregarded, received antiviral treatment, although RNA HCV remained positive. In the control group, 141 cases were positive for HCV antibodies (prevalence 0.24%). The prevalence in the study group was significantly higher (p < 0.001). CONCLUSIONS HCV is more prevalent in patients with Gn than in those without, and this is the opposite of the situation with HBsAg.