Almost 27 million children in the U.S.--or 42 percent of those under age 18--had mothers working or seeking work in March 1974. About one in four of these children (6.1 million) were below regular school age. Since 1970, the number of children whose mothers were in the labor force has risen sharply by 1.2 million, while the total number of children in families has dropped by 2.2 million. The absolute increase in the total number of children with working mothers occurred almost exclusively in female-headed families. Over 12 million children were in families where the father was either absent (8.6 million), unemployed (1.5 million), or not in the labor force (2.0 million). Included are three tables: (1) number of children under 18 years old, by age, type of family, labor force status of mother, and race, March 1970 and March 1974; (2) number of families and average number of own children under 18 years old, by type of family, labor force status of mother, and race, March 1970 and March 1974; and (3) number of children under 18 years old, median family income in 1973, type of family, labor force status of parents, and race, March 1974. (Author/NH)