INTRODUCTION: Exercise during pregnancy is associated with reduced rates of preeclampsia, gestational diabetes, anxiety, insomnia, and excessive weight gain. Continued exercise during the postpartum period is important for healthy weight loss and reduced anxiety. Unfortunately, pregnant and postpartum women are significantly less active than nonpregnant women. The purpose of this pilot study was to evaluate a telephone-based exercise intervention designed for pregnant and postpartum women. METHODS: Healthy women (N = 37) who were pregnant (16 weeks' gestation or less) or postpartum (6 months or less) participated in a 3-month, telephone-based exercise intervention based on the transtheoretical model and social cognitive theory. Exercise was assessed by using the 7-Day Physical Activity Recall Interview. RESULTS: Pregnant participants significantly increased their exercise from a mean (standard deviation [SD]) of 60.47 (63.1) minutes per week at baseline to 132.9 (82.3) minutes at 3 months, F(1,13) = 9.96, P < .01. Postpartum participants significantly increased their exercise from a mean (SD) of 68.9 (63.5) minutes per week at baseline to 123.8 (48.8) minutes at 3 months, F(1,15) = 6.56, P < .05. DISCUSSION: Participants responded positively to the intervention by significantly increasing their exercise levels. There is a need for a large, randomized controlled trial examining the efficacy of telephone-based exercise interventions for pregnant and postpartum women.