A burgeoning body of research documents links between sleep and adjustment in adolescence, but little is known about the role of the social ecology in promoting healthful sleeping habits. This study was aimed at identifying the socio-cultural correlates of adolescents' sleep, including average nighttime sleep duration, average daytime napping, and night-to-night variability in sleep duration and assessing the links between these dimensions of sleep and adjustment in Mexican-American youth. Participants were 469 Mexican-American adolescents (50.5 percent female) and their mothers and fathers. Data on family socio-cultural characteristics and youth adjustment were collected in home interviews with youth, mothers, and fathers, and, during seven evening telephone interviews, adolescents reported on nighttime sleep and daytime napping for the prior 24-h period. Night-to night variability and napping were more strongly linked to youth depressive symptoms and risky behavior than was average nighttime sleep, whereas nighttime sleep predicted lower body mass index. Lower parental acculturation and fathers' familism values predicted more healthful sleep, and higher levels of family income, parental education and neighborhood crime predicted less healthful sleep. In addition to illuminating the significance of socio-cultural influences on youths' sleep, this study contributes to the literature by documenting the multidimensionality of sleep patterns and their links with adjustment in an understudied population. (Published Abstract)