Overcrowding has been unable to exert a predominating influence on the course of tuberculosis. Overcrowding is the most mischievous factor of town life. This chapter shows the difference in overcrowding between urban and rural communities in England and Wales. Compared with 1891 marked improvement had occurred in overcrowding in towns, but very much more in the country districts. In the case of Ireland, the relations between overcrowding and tuberculosis are masked completely. In Paris the conditions of housing are extremely bad, and the phthisis death-rate is high and probably almost stationary. In view of the known pathology of the disease, no circumstance could be more calculated to exercise a uniformly adverse influence on this disease than overcrowding. Overcrowding must therefore be classed with urbanisation as a factor which, though of proved effect on the phthisis rate, has usually been unable to overcome counteracting influences by which the phthisis rate has been diminished.