Technical Abstract: The USDA’s Automated Multiple Pass Method (AMPM) is a five-step, multiple-pass, interviewer-administered, computerized, 24-h dietary recall. The objective of the study was to quantify sources of variation such as day of the week, season, sequence of the diet interviews (training effect), diet interviewer, body weight, and within- and between-subject variance in intake of selected nutrients and the number of 24-h dietary recalls required to obtain accurate estimates of intake in obese adults. The 24-h dietary recalls were obtained every 10 days for six months using the USDA’s AMPM. Variance component estimates were made using a mixed model procedure. Two approaches were used to determine the number of days of the 24-h dietary recalls that are required to estimate usual energy and nutrient intake. Obese subjects (34 men, 39 women) completed at least 14 dietary recalls and 70% completed 15. Within- and between-subject variances were the major contributors to variance in nutrient intakes. The training effect of repeated dietary recalls over time and individual diet interviewer effects had little impact on variance. Due to within- and between-subject variances, it required 2 to 4 days and 3 to 6 days in men and women, respectively, to accurately estimate energy and macronutrient intake over a six month period. Among individuals, day-to-day changes were the major contributors to variance in nutrient intake, whereas methodological components did not influence variances, thus demonstrating the utility of the USDA’s AMPM. The number of 24-h dietary recalls required to estimate intake is dependent upon the degree of accuracy required and the typical variability in consumption of the nutrient of interest.