Fluorescein-conjugated, type-specific monoclonal antibodies to herpes simplex virus (HSV-1 and HSV-2) and group-specific antibody which recognizes both HSV-1 and HSV-2 were used to detect HSV-infected cells in clinical specimens. Specimens were collected from 66 pregnant women with a past history of herpes genitalis or with suspected lesions. Fourteen of 18 samples from which virus was isolated were positive by immunofluorescence test; four of 18 specimens had an insufficient number of cells (less than 50 per smear) for analysis. In one specimen, a positive reaction by immunofluorescence was not confirmed by virus isolation. HSV was typed directly on smears of clinical specimens in 14 instances: three samples were identified as HSV-1, and 11 as HSV-2. Moreover, the immunofluorescence test was used to type HSV isolates in cell cultures in these cases and 40 additional strains. Examination of viral deoxyribonucleic acid fragments obtained by restriction enzyme digestion confirmed the typings; complete agreement was found among the three methods. Immunofluorescence with monoclonal antibodies is a reliable test for rapid diagnosis and simultaneous typing of genital HSV infections, even in asymptomatic women. With adequate specimens, the specificity and sensitivity of this method approach 100%.