This brief uses data from the 1997 National Survey of America's Families to count the number of people living in low-income working families and to describe their personal characteristics and jobs. It examines: what low-income working families are; who the family members are; and how much low-income workers work and at what jobs. One in six nonelderly Americans lives in a working low-income family (having income below twice the federal poverty level and all adults working at least half-time). Almost two-thirds of low-income families include children and two adults. The major differences between incomes of working low-income families and higher-income families are substantially lower hourly earnings plus fewer secondary workers and lower work effort among secondary workers. If all prime-age adults worked full-time, full-year, about one-fifth of working low-income families would become higher-income families, and more than one-third of other low-income families would become working low-income families. Even if policies promoting work successfully increase work effort, many people will still live in working low-income families. Lifting working families above the poverty level requires better wages and work supports. (SM)