A broadly based epidemiologic investigation of cervical cancer, with special reference to the herpesvirus hypothesis, was recently completed in Yugoslavia. A total of 350 women < 65 years old with histologically confirmed squamous carcinoma of the uterine cervix and an equal number of other currently hospitalized women were interviewed, examined, and bled for measurement of neutralizing antibodies to oral (HSV-l) and genital (HSV-2) herpesviruses. No pattern was discernible in the distribution of HSV-l titers. However, for both Moslems and non-Moslems in each age group studied, as well as in all combined, HSV-2 titers were higher among cases than controls. The ratio of HSV-2 to HSV-l mean log titers was also significantly higher in each group of cases than in the corresponding controls. Furthermore, HSV-2 antibody prevalence- as judged by II /I titer ratios > 84-was significantly greater among cases than among controls, both Moslem and non-Moslem, with a relative risk of approximately 2. It is the consistent direction of these findings, rather than their absolute numerical value, that is regarded as most impressive. The results of this investigation lend further credence to the herpesvirus hypothesis in cervical cancer.