1. The day-to-day records over a period of 4–6 months of 167 normal women's physical changes and subjective phenomena have been collected by a new method. These women submitted data from 780 complete menstrual cycles. In addition, a smaller group submitted data which have been used for physical changes only. One woman's individual record of certain phenomena was obtained over a period of 8 years.
2. The average length of the menstrual cycle was 27·8 days with a standard deviation of 3·4 days. Some individual's cycles were characteristically short or long, regular or irregular. No woman menstruated with complete regularity (measured in days) over a period of 6 months. Twenty-three per cent of the menstrual periods began between 7.30 and 9.30 a.m., and the average duration of the flow was about 4·5 days.
3. Records from one case of intermenstrual, probably ovulatory, bleeding were obtained over a period of 6 months (Chart 2).
4. The periodicity of each subjective phenomenon as shown by the combined results has been recorded graphically, and these figures themselves constitute a summary of the results. Thus for fatigue, abdominal pain, backache, headache, breast changes, sexual feeling and intercourse, depression, elation, tendency to cry, irritability, intellectual capacity and tension see Figs. 5–19. Individual data of interest have been discussed in the light of the combined results.