Objective: This is the first of two related articles on a study carried out between 2000 and 2003 designed to assess the prevalence, associated comorbidities, and correlates of disruptive behavior disorders in two populations of Puerto Rican children: one in the Standard Metropolitan Areas of San Juan and Caguas in Puerto Rico, and the other in the south Bronx in New York City. Method: This article provides the study's background, design, and methodology. Probability samples of children ages 5 to 13 years were drawn at the two sites (n = 2,491). Subjects and their primary caretakers were interviewed using the Diagnostic Interview Schedule for Children-IV and a wide array of risk factor measures. The samples were weighted to correct for differences in the probability of selection resulting from sample design and to adjust for differences from the 2000 U.S. Census in the age/gender distribution. Results: The samples are representative of the populations of Puerto Rican children in the south Bronx and in the Standard Metropolitan Areas in Puerto Rico. Of the 2,940 children identified as eligible for the study, 2,491 participated for an overall compliance rate of 85%. Conclusions: The study results, to be described in an accompanying report, are generalizable to the two target populations. (Contains 4 tables.)