['Parvovirus B19 has been demonstrated in testes of patients with germ cell tumours but not in controls, raising the possibility that the virus has an aetiological role in these tumours. The aims of this study were to investigate the association of the virus with germ cell tumours and to localise the virus histologically.', 'DNA was extracted from paraffin wax embedded sections of testes from 10 seminomas, eight teratomas, two mixed seminoma/teratomas, and 10 testes showing benign histology. Polymerase chain reaction (PCR) amplification of three regions within the NS and VP1/2 genes was carried out in duplicate on all samples. One PCR positive case (seminoma/teratoma) was examined by microdissection of histologically defined tissue components followed by PCR amplification of parvoviral sequences. Samples from PCR positive patients were immunostained using a B19 specific monoclonal antibody.', 'Seven cases were PCR positive, these comprised two of 10 seminomas, one of two mixed tumours, none of eight teratomas, and four of 10 benign controls. PCR analysis of the material microdissected from the seminoma/teratoma showed the presence of the virus in regions of seminoma, teratoma, intratubular germ cell neoplasia, normal tubules, and connective tissue. All patient samples studied immunohistochemically were negative.'] Is parvovirus B19 associated with benign testes as well as testicular germ cell tumours?