This study presents data from the 1979 Income Survey Development Program (ISDP) on lifetime work interruptions and examines the relationship between work interruptions and earnings. Descriptive data showing the extent to which men and women have experienced work interruptions are presented, followed by an analysis of the impact of work interruptions on earnings. The tables in the report show the proportion of persons with work interruptions and the proportion of potential work years spent away from work for the reasons surveyed. Work interruptions were reported by sex; by race and Spanish origin; by years of school completed; by occupation; and by life-cycle status. The data were gathered by a panel survey of approximately 9,000 households that were visited at three-month intervals over a period of a year and a half beginning in February, 1979. The data were then inflated to represent the civilian noninstitutional population of the United States and members of the armed forces living off post or with their families on post. The data presented cover persons 21 to 64 years of age who ever worked. (The study concludes that work interruptions explain only a small proportion of the earnings differential between men and women.) (KC)