With the use of data from the Spring 1977 sample of the USDA Nationwide Food Consumption Survey 1977-78, 1- and 3-day nutrient intakes for 8,779 individuals in 22 sex-age groups in the 48 conterminous states were compared. For most nutrients studied, 3-day mean intakes and day 1 mean intakes showed little difference. Mean intakes for day 1 and for days 2 and 3 combined were not significantly different for most sex-age groups for most nutrients. The few statistically significant differences observed for energy, fat, and carbohydrate could have been the result of chance and therefore have little practical significance. Regression analysis indicated that day 1 intake was strongest as a predictor of intake on subsequent days for energy, carbohydrate, calcium, magnesium, and phosphorus; less strong for protein, fat, iron, thiamin, riboflavin, niacin, vitamin B-6, and vitamin C; and poorest for vitamin A.