This longitudinal study examined the association between heavy alcohol use, alcohol- and drug-screening requirements, and social support network variables and mothers' welfare participation in the United States. The study was a secondary data analysis of 3,517 mothers. The sample was extracted from National Longitudinal Survey of Youth data gathered in 1994-2004. Results of logistic regression show welfare participation is not associated with heavy alcohol use or alcohol- and drug-screening requirements, but is associated with a history of reported heavy alcohol use, informal help with childcare, and scant human capital. Results also indicate that alcohol- and drug screening required under TANF may not exclude heavy drinking mothers from TANF participation, and that social support networks do not cancel heavy drinking's association with participation. Policy implications are discussed.