First published in 1978, Once A Month was the breakthrough book that introduced the world to Premenstrual Syndrome. Dr. Katharina Dalton challenged an entire medical tradition that dismissed premenstrual symptoms as "in a woman's head," and showed that PMS is a real - and treatable - condition.

Dr. Dalton has treated over 50,000 women with PMS, and this fifth edition is based on her wide experience and the latest research. There is new information about the role of diet in managing PMS symptoms, and a special chapter on the experiences of women who have dealt with premenstrual syndrome for the last 30 years.