The second component concerned appropriate measures of social class for studies of women's health. It used data on 718 women who participated in Examination II of the Kaiser Permanente Women Twins Study (1989-1990) . Socioeconomic information existed on: adult individual and household class (which took into account the individual class position of both the respondent and her partner or head-of-household, if present), childhood household class, and class trajectory (comparing childhood and adult household class). Data on health characteristics included: blood pressure, body mass index, waist-hip ratio, lipoprotein fractions, fasting and postload insulin and glucose serum concentrations, self-assessed health status, age at first completed pregnancy, total number of childbirths, duration of breast feeding, physical activity, and smoking status. Analyses evaluated whether different magnitudes of class-based differences in these health characteristics were detected with these diverse measures of social class, using multivariate techniques that corrected for the correlation of errors within twin pairs. The effects of using these different class measures were also examined for analyses testing the hypothesis that social class was inversely related to risk of hypertension among women, adjusting for relevant covariates.