Little information is available concerning the effects of jogging during pregnancy on fetal and maternal outcomes. Through the use of a questionnaire, data were obtained on 67 experienced runners who continued to jog during pregnancy. The women had been running for an average of 3.8 years before the pregnancy, and ran an average of 470 miles during the pregnancy. The average number of miles run decreased as the pregnancy progressed (P < .05). There was no correlation between the number of miles run during the pregnancy, or in the third trimester alone, and either infant birth weight or gestational age. The incidence of maternal and fetal complications was low. Although there are limitations with questionnnaire retrospective studies, these data suggest that jogging during pregnancy by healthy women accustomed to such activity is not harmful to the infant.