Human cytomegalovirus (HCMV) has been suspected to participate in the pathogenesis of IgA nephropathy (IgAN). However, with regard to the presence of HCMV in the renal tissue of IgAN, conflicting results have been reported using a variety of different techniques. Renal biopsies of 29 patients with IgAN, of 7 with focal segmental glomerulosclerosis (FSGS) and of 11 normal kidneys were analyzed for the presence of HCMV-DNA using the polymerase chain reaction. HCMV-DNA was detected by hybridization with digoxigenin-labelled probes in 14 of 19 analyzed frozen renal biopsies from patients with IgAN. However, only 1 of 17 renal biopsies of IgAN embedded in paraffin was positive for HCMV-DNA. Furthermore, HCMV-DNA was detected in 4 of 18 frozen normal kidneys but in none of the tissues from patients with FSGS. The present results provide further evidence of an association between the presence of HCMV in renal tissue and IgAN.