Of the world's largest child labor force in India, Bombay has over 30,000 working children, most of them migrants. In a prospective study of 73 working children from a part of Dharavi, the biggest slum in Asia, 68% were working as hotel boys; 22% had started working before their 10th birthday, a large number doing so to increase the family income, but earning less than Rs. 100 ($11) per month. Forty percent worked more than 12 hours a day and only 16% continued schooling. Two-thirds depended entirely on their employers for food which was adequate and no child in the study was malnourished. Overall incidence of anemia and vitamin deficiency was 10% each. Only 7% had ailments related to their occupation. Because this was a cross-sectional study no conclusions can be drawn regarding long term and residual effects. Preventing children from working is likely to make worse their own as well as their families' problems unless substitute sources of income or welfare are available. Legal protection and other services near their working places are essential for those who have to work.