This study examined factors associated with lifetime experience of homelessness among young adults. Data were analyzed for 14,888 young adults (mean+/-SD age 21.97+/-1.77; 7,037 men and 7,851 women) who participated in the National Longitudinal Study of Adolescent Health (Add Health), a U.S. nationally representative, population-based sample. Data were collected from young adults through computer-assisted interviews six years after they had enrolled in the study as adolescents. Variables that have been associated with lifetime homelessness in at least one service sample were mapped to Add Health survey items. Data were analyzed by logistic regression. A total of 682 respondents (4.6%) were classified as ever being homeless. Several factors related to childhood experiences of poor family functioning, socioeconomic disadvantage, and separation from parents or caregivers were independently associated with ever being homeless. Other significant independent factors included current socioeconomic difficulty, mental health problems, and addiction problems. Indicators of involvement in crime and addiction problems with gambling and alcohol were not independently associated with homelessness. The findings underscore the relationship between specific indicators of adversity in childhood and risk of homelessness and point to the importance of early intervention efforts. Consistent with the extant research literature, mental health problems also appear to be associated with homelessness, highlighting the potentially complex service needs of this population.