Fourteen perimenstrual symptoms were rated daily by 33 women in a randomized, double-blind, crossover trial of calcium supplementation. Factor analysis was performed on these symptoms using 2,413 daily ratings during the luteal and menstrual phases with at least one symptom present. Four factors (negative affect, water retention, food, and pain) accounting for 67 percent of the total variance were extracted. Internal consistency was high for scales based on these factors. Correlations between the scores ranged from .35 to .69. Scores were low during the intermenstrual phase and much higher during both luteal and menstrual phases. Paired t-tests comparing the intermenstrual phase with both luteal and menstrual phases all resulted in significant differences at p less than .01. There was more pain reported during the menstrual compared with the luteal phase (p less than .01). Calcium supplementation reduced negative affect (p = .045), water retention (p = .003), and pain (p = .036) during the luteal phase and pain (p = .02) during the menstrual phase.