A continuing study of the frequency of primary drug-resistance among tuberculous children in a community of low socioeconomic status was made during a period of short-term hospital treatment for adults (1969–1971) and compared to the frequency of primary drug-resistant disease observed among children with tuberculosis who were admitted to the hospital during 2 prior periods of study that corresponded to long-term hospital care of the adults (1961–1964 and 1965– 1968). There was a significant increase in the frequency of strains with primary resistance to streptomycin (16.4 per cent) and a tendency toward an increase in the frequency of strains with primary resistance to isoniazid (13.5 per cent) among the children admitted to the hospital during the present study compared to the 2 previous studies. The increase in the proportion of isoniazid-resistant strains, however, was not significant, and the rate of increase in streptomycin-resistant strains during the present study was not greater than that for the...