A review was made of the outcome of 644 pregnancies in 228 women with cytologically detected genital herpetic infection, 224 pregnancies in 100 women with negative herpes smears, and 2791 pregnancies in the general hospital population. A significantly higher abortion rate (33.3%) resulted from pregnancies occurring in women after detection of their genital herpetic infection than from pregnancies occurring before the infection was detected (10.8%) or from those in the control group (9.4% and 11.5%). In 21 women with genital herpes detected during the first 4 months of gestation, seven pregnancies terminated in abortion. These observations suggest an association of genital herpetic infection with abortion and point to the need for concerted virologic, clinical, and pathologic studies to provide further evidence of this association and an understanding of the possible mechanisms involved.