Introduction. About 80% female school students suffer dysmenorrhea and sometimes experience a decrease in academic performance due to dysmenorrheal pain. Warming the abdomen has been widely used for pain relief as a non-pharmacological method. The heat- and steam-generating (HSG) sheet, which keeps the attached skin area around 40°C for 5 – 8 hours, relieves dysmenorrheal pain with comfort (Hosono, 2010). The comfort may promote the intellectual ability and thus prevent such a decrease in academic performance. The aim of this study was to clarify the effects of abdominal warming using the HSG sheet on the intellectual ability during simple calculations. The protocol of this study was approved by the local ethics committee. Methods. Ten female university students (age 21.5 ± 0.4, mean ± SEM) were included in this study. During menstruation periods, a subject sat in a room of 25°C and attached an HSG sheet (HSGS group) or a non-warming sheet (NWS group, control), as large as the HSG sheet, to the lower abdomen. Measurement was performed only once during a subject’s menstruation. When a subject participated in HSGS at the first measurement, the subject participated in NWS in the next menstruation. For the evaluation of the intellectual ability, we used a randomly generated simple single-digit addition similar to the Kraepelin psychodiagnostic test. The subject performed the test just before and 1 hr after attaching the HSG sheet. The subject solved as many questions as possible for 15 min. We counted the number of correct answers (A) per total number of answered questions (B), and obtained the solution rate (SR) as A/B x 100. We also measured the thumb temperature (Tt) for evaluating sympathetic nerve activities (SNS). The subject also recorded her dysmenorrheal pain level using a integral score of zero (no pain) to three (severe pain). Results. The SR in the HSG group (32 ± 25%) significantly increased (p<0.05, Wilcoxon signed-rank test) compared to the control (-3 ± 9%). The increase rate of SR in the HSGS was significantly higher than in the NWS. The rate of subjects with pain scores of more than two after 1-hr HSG sheet application was also significantly lower (Fisher’s exact test, p<0.05) in the HSG group (50%) than in the control group (71%). The Tt in the HSGS (33.9 ± 1.3°C) was higher than in the NWS (25.6 ± 3.6°C), indicating a decrease in SNS. Discussion and Conclusion. Lower abdominal warming using the HSG sheet was effective for increasing intellectual activities. Interestingly, although three of the subjects did not feel dysmenorrheal pain during the measurements, all of them also experienced an increase in SR. Thus, the increased intellectual activities may not be completely due to only relief from dysmenorrheal pain. The increase in intellectual activities might be related to SNS decrease.