This study was directed toward investigating effects of menstrual cycle stages and caffein ingestion on various physiological and psychological processes. Subjects maintained a daily log of basal waking temperature (BWT), occurrence of menstruation, and consumption of caffein containing beverages and medications. At each session, visuo-spatial discrimination, depth perception, and time estimation (15 and 30 sec) were assessed. The Menstrual Distress Questionnaire (MDQ), The Measurement of Depression (MOD), and a self-report scale were completed.Multiple linear discriminant analyses were conducted on menstrual cycle and caffein ingestion data. Variables that contributed significantly to the discrimination of level of caffein ingestion were visuo-spatial discrimination; MDQ Water Retention and Control; cervical, lumbar, and saccral temperatures; time required to reach baseline; and total daily consumption of caffein-containing beverages.