The penetration of cephapirin sodium into tissues that are commonly involved in gynecologic infections was studied after administration of a single i.v. dose of 1 g of cephapirin to about 15 patients to undergo gynecologic surgery. Blood and tissue specimens were obtained either 30 or 60 min after the infusion had been completed. Blood levels averaged 16.07 +/- 3.7 and 6.29 +/- 1.6 microgram/ml and mean tissue levels were 7.87 and 6.28 microgram at these two sampling times, respectively. These results suggest that bactericidal levels of cephapirin against sensitive organisms can be achieved in gynecologic tissues.