Cell cultures originated from human foreskin (HFS) tissues were used for isolation of viruses from diagnostic specimens. The foreskins were collected in Hank's balanced salt solution and then processed on the same day by dispersion in trypsin. A week after the trypsin treatment of the tissues, the first cell cultures were ready to use. Continuous subcultures in vitro of the cells gave rise to a colony of cells that multiplied freely in vitro and supported the growth of viruses from the herpes group. In three cases tested in our laboratory in the last 6 months, viruses from the herpes group were isolated on the HES. The cytopathic changes of the HFS cells were observed 5 to 8 days after infection. They were not detected on two other human-origin cell cultures (WI-38 and HEp2) or on primary monkey kidney cells. The viruses isolated from these three cases were cytomegalovirus (CMV) from urine of a 2-week-old baby, a second CMV from a cutaneous lesion of a renal-transplant patient and herpes simplex virus from the eye swab of a young girl. After a few subcultures on the HFS cells, the three viruses produced CPE on the other susceptible human cells. The preparation of HFS cells is easy, the availability of the tissue is high, and the diagnostic value is unquestionable. It is suggested that this tissue and its cell cultures be used more often in diagnostic and research laboratories.