In 1976, 121,700 nurses ages 30-55 completed and returned the initial Nurses Health Study questionnaire and comprise the Nurses Health Study cohort. The cohort has been followed by means of biennial mailed questionnaires. A total of 109,413 participants responded to the 1978 questionnaire. In addition, 400 women who replied in 1976 stated that they did not wish to continue in the study and 390 women died. In 1980, the first major dietary assessment was added to the questionnaire. In the 1978-1980 interval, there were 624 deaths, 300 women declined further participation, approximately 99,000 completed the full questionnaire including the dietary questionnaire, and another 4,000 completed an abbreviated questionnaire, for a total of about 103,000 responses. In 1982, the overall response was 101,174. The approximately 19,000 living non-respondents were followed by telephone, yielding 71 percent of the non-respondents. Thus, at the end of 1982, current information was available on 116,150 or 95.4 percent of the original cohort.