This report clarifies the discussion and debate over what constitutes a low-income working family, documents the size and characteristics of low-income working population, and examines their incomes and expenditures. Using data from the 2002 round of the National Survey of America's Families (NSAF), we find that low-income families (income below twice the federal poverty line) with at least one full-time, full-year worker have incomes that are roughly in line with their basic expenses thanks to their work effort, earned income, and a generous refundable Earned Income Tax Credit; however, low-income families without a full-time, full-year worker do not appear to have enough income to cover their basic expenses.