A prospective study was performed of 152 pairs of nonstress tests (NSTs) obtained simultaneously from both members of 52 twin gestations. Fifty-seven percent of the total fetal heart rate (FHR) accelerations occurred simultaneously in both twins. Between twins, the incidence of simultaneously occurring FHR accelerations was independent of gestational age, growth discordancy, or the type of placenta. For each twin, the number of FHR accelerations remained constant with increasing gestational age. These results may suggest that tactile communication exists in utero between twins.