Prevention of early weight gain may be critical to avoid relapse among women with a fear of weight gain. Menstrual phase has physiological fluctuation of fluid resulting in short-term weight gain, suggesting menstrual phase of smoking cessation may impact short-term weight gain. This study examined the effect of smoking abstinence and menstrual cycle on short-term weight gain. Women were randomized to quit smoking during the follicular or luteal phase of their cycle and followed for four weeks. Weight, among other measures, was recorded at five post-quit date visits (days 2, 5, 9, 12 and week 4). Participants (n=152) were grouped based on randomized quit phase and smoking status after assigned quit date: 1) follicular (F), quit < 24 h, 2) F, quit > or = five days, 3) luteal (L), quit < 24 h, and 4) L, quit > or = five days. Participants who quit smoking experienced significantly more weight gain than those who quit for less than 24 h. There were no significant increases in short-term weight gain based on menstrual cycle phase during attempted smoking cessation.