We mailed a health survey to the 18,408 residents of a California retirement community and compared the 11,550 respondents on a number of characteristics by time of response. Early respondents were more likely to be the "worried well," that is, healthy individuals who see their doctor regularly, receive disease detection screening, and follow healthful life-style practices. Late respondents tended to answer questions regarding their mental function and emotional status more negatively. Early and late respondents did not differ in the rates of death or hospitalization during the first 5 years of the study; nonrespondents had a higher incidence of hospitalization than respondents in year 1 and higher death rates in the first 3 years, but not thereafter.