OBJECTIVE: Because women with late luteal phase dysphoric disorder (LLPDD) experience symptomatic affective states predictably, they can be studied to determine whether there are biological findings related solely to the clinically symptomatic state. The authors sought to answer the question, Does body temperature change with affective state? METHOD: The core body temperature and motor activity patterns of 10 women with premenstrual syndrome (PMS), six of whom also met criteria for LLPDD, and no other psychological or medical illness were compared to those of six women with chronic, noncyclic dysphoria and six asymptomatic comparison women at four phases of the menstrual cycle. RESULTS: The nocturnal temperatures of the women with PMS/LLPDD were significantly higher than those of the comparison subjects across the entire menstrual cycle, but there were no differences in nocturnal activity levels. The women with noncyclic dysphoria had a mean nocturnal temperature in the follicular phase as high as that of the women with PMS/LLPDD. The temperatures of all women were higher in the luteal phase than in the follicular phase. CONCLUSIONS: These findings suggest that in the future investigators should document menstrual cycle phase in all female subjects and, when studying body temperature, should carefully monitor symptomatic state in comparison subjects.Abstract Teaser