Chilliness is a common complaint among menopausal women. Increasing evidence indicates that young women also suffer from chilliness, resulting in decreased learning, motivation, and concentration. Neither diagnostic criteria nor drug therapies exist for chilliness, and thus, young women suffer from insomnia, fatigue, and mood disturbance. Because chilliness is correlated with hormonal changes observed during premenstrual, postpartum, and menopausal periods, reproductive hormones are likely involved. Recently, we elucidated methodological issues related to identifying young women with chilliness.