For many caregivers, rendering aid to frail parents, grandparents, siblings, and spouses comes at a high price: compromised physical and mental health, disturbed relationships with spouse and children, truncated opportunities for social life, and, for caregivers who are employed, declining job performance. Using the 1982 National Long Term Care Survey's "Survey of Informal Caregivers," this study investigates how the sociodemographic characteristics of caregivers, care requirements, the availability of backup caregivers, and conditions of employment affect the likelihood that caregivers will suffer work constraints. Estimations of both the probability of work constraints and hours of work reveal that proxies for work conditions figure prominently, as do care requirements. In the model of constrained work, ill health, financial burdens, and primary responsibility for care are significant determinants; the estimation of hours of work revealed that low income and competing care demands wielded major influence. Women and white caregivers are employed fewer hours, while spouses are more likely than other informal caregivers to face constrained work. Occupation. as an indicator of work conditions, is shown to be an important addition to the factors considered in investigations of circumstances that affect caregivers' experiencing work constraints.