Studies of the prevalence of substance abuse among welfare recipients have varied widely in their findings, with rates of between 4 and 37 percent reported. Much of the difference in prevalence rates found in these studies is due to different data sources, definitions and measurement methods, particularly the different thresholds used to define substance abuse. Another key difference is whether alcohol abuse and/or the abuse of prescription drugs are included in the estimate. In addition, drug use and abuse is higher among single men in States’ General Assistance (GA) caseloads than among single (largely female) parents on TANF.