The distribution of various infectious diseases in certain training centres is discussed inrelation to the streptococcal aetiology of acute rheumatism, and the relative importance of age and environment are noted.

It gives me real pleasure to acknowledge the interest and support of Vice-Admiral Sir Percival Nicholls, K.C.B., and Vice-Admiral Sir S. F. Dudley, K.C.B., F.R.S., throughout these investigations which were facilitated by the willing co-operation of numerous officers and personnel of the R.N. Medical Service. To Surg. Capt. F. Hitch and the staff of the R.N. Medical School I am greatly indebted, particularly for the efficient technical assistance rendered by Petty-Officer L. Waller. The work was carried out during tenure of the Erederick Pearson-Sir Halley Stewart Naval Research Fellowship of the Empire Rheu-matism Council.