For three years the Air Pollution Medical Branch of the Division of Special Health Services has been working in the increasingly more important but relatively unexplored field of air pollution as it relates specifically to human health. The work began with a search for, and a systematic appraisal of the scattered sources of available knowledge, followed closely by tentative explorations into those portions of the problem holding promise of significant findings. The results of the early activity proved sufficiently successful to help in charting the present course of action which, in turn, appears to be pointing toward those areas which will require emphasis in the future.