This study, conducted 1977–1979, was designed to assess the extent to which spouses share similar nutrient Intakes, and to determine whether con clusions based on spouse-substituted nutrient intake data in investigations of diet-disease associations could be misleading. The study sample consisted of 1428 married couples aged 45 years and older belonging to the five major ethnic groups (Caucasians, Japanese, Chinese, Filipinos and Hawailans/part Hawalians) residing on the island of Oahu, Hawaii. Caloric and nutrient data were derived from quantitative intake of 83 food and beverage items that had been selected to cover the main sources of dietary fat and protein (representing 85–90% of total intake), giving somewhat less complete information on carbohydrate and vitamins C and A. Statistical analyses were based on absolute nutrient consumption as well as on consumption per kilogram of body weight. As a group, hu8bands consumed substantially more calories, protein, fat, carbohydrate, cholesterol and vitamin A, but slightly less vitamin C than did the wives. Per unit of body weight, there was no noticeable husband-wife difference for any nutrient Item except vitamins A and C, which were consumed more by the wives. Within-spouse-pair analysis showed a moderate extent of husband-wife correlation In the consumption of each nu trient item, as measured by the intraciass correlation and Spearman's rank correlation. Whereas the intraciass correlations were generally higher when consumption was corrected for body weight, the reverse was true for the rank correlations. These resuits suggest that spouses exerted a moderate but definite mutual influence on dietary intake. However, linear regression analysis of the wives' consumption (dependent variable) on the husbands' consumption (independent variable) showed the regression coefficient to be substantially less than unity (p < 0.001) for all nutrient items, whether or not correction for body weight was made. Hence, the magnitude and even direction of the husband-wife difference in nutrient intake were not consistent among different couples (i.e., among the couples where the husband's intake was low, the wife tended to have a higher intake than the husband, and vice versa). These resuits Indicate that the use of nutrient Intake data substituted from one spouse as a reflection of the other may lead to erroneous conclusions. Ethnicity, age, socioeconomic level, and whether the marriage was ethnically homogeneous or mixed, did not materially affect the husband-wife relationship in nutrient intake. Also, the statistical results for those couples where one member (usually the wife) responded for the other spouse were not materially different from those couples where each member responded individually.