Summary. The reported association between genital infection by herpes simplex virus (HSV) type 2 and cervical neoplasia has been investigated at a molecular level. Tissue culture of over 50 cervical cancers resulted in the development of several cell lines but none of these expressed HSV information. The permanent cell line, Cxl06, which was generated was found to contain multiple genome copies of human papillomavirus (HPV) type 16. Southern blot analysis of nine cervical cancers showed an authentic 2.8 Kb fragment of HSV-2 DNA in one of the tumours. This piece of viral DNA maps in a morphological transforming region of the HSV genome. Superinfection of cervical cancers with temperature-sensitive (ts) mutants of HSV 1 and 2 did not generate recombinant virus, suggesting that HSV DNA was not present in the tumours studied. An attempt to identify latent HSV close to the cervix in organ cultures of uterosacral ligament tissues resulted in reactivation of virus in several instances. These results are discussed against a background of decline in acceptance by many, for the HSV link with cervical cancer, and the dramatic impact of the discovery of a close relation between HPV type 16 and lower genital tract neoplasia.