This analysis examines poverty in families headed by working single mothers, addressing whether and to what degree their economic situations have improved. It investigates the effect of the 1996 Personal Responsibility and Work Opportunity Reconciliation Act, which moved single mothers from welfare to work. Poverty data from the annual Census Bureau Current Population Survey for 1993-99 were used. No progress was evident in reducing poverty between 1995-99 in families headed by working single mothers. Poverty rates for families with children not headed by single mothers dropped from 1993-99. The poverty gap in families headed by working single mothers grew larger since 1995. A major factor in the lack of progress in reducing poverty in this group after 1995 was the contraction of certain government safety net programs. Declines in the anti-poverty impact of government benefit programs occurred despite the increasing effectiveness of the Earned Income Tax Credit in reducing poverty among people in working single mother families. After 1995, declines in the effectiveness of the safety net in reducing poverty among these families offset the effect of the improving economy, halting the reduction of poverty rates for those families and pushing those who remained poor deeper into poverty. (SM)