Not long ago we reported the result of prophylactic therapy for rickets in a negro community.1This test was carried out in what is known as the Columbus Hill district of New York City, a district with a population of about 9,000, composed almost entirely of negroes. As was stated in the previous paper, this section enjoys the unenviable distinction of having the highest infant mortality rate of any community in the city, although, it should be added, the rate is steadily decreasing. Shortly before we undertook this study, a survey of Columbus Hill had been carried out by the Henry Street Settlement and the National League for the Study of the Urban Conditions of the Negro, to ascertain the social and economic conditions responsible for the high death rate. Both these organizations have been helpful in enabling us to gain access to the homes of these people, and