BYS is a longitudinal study of antisocial behaviours and other psychiatric disorders among Puerto Rican children living in the South Bronx of New York City (being raised as a minority), and in the Standard Metropolitan Area of San Juan and Caguas, Puerto Rico (being raised as a majority). Almost 2,500 children between the ages of 5 and 13 were recruited from multistage probability household samples representative of the two target populations in New York and Puerto Rico. The sample included 1,138 child-parent dyads in the South Bronx and 1,353 child-parent dyads in Puerto Rico. Up to three children per household were recruited, resulting in a total of 2,491 children from 1,643 households. The children and their caregivers were followed up annually for 3 years during childhood/early adolescence (between 2001 and 2004), and once in late adolescence/early adulthood (between 2013 and 2017). As the original BYS participants become adults and have children of their own, the study is aiming to recruit and follow up the next generation (Generation 2; G2) of BYS as part of the Environmental Influences on Child Health Outcomes (ECHO) Program.