Rheumatic fever and diabetes mellitus rarely coexist (Joslin et al., 1952). An opportunity to investigate this unusual combination of disease was provided by a young male diabetic (Case 1), known to take insulin. who was receiving full salicylate treatment for acute rheumatism when admitted to hospital. At the outset we were confronted with a problem, for his urine was sugar-free and the fasting blood-sugar level was normal, though he was receiving only aspirin. The possibilities first entertained were that the previous diagnosis of diabetes was in-accurate or that spontaneous remission of the disease had occurred: neither seemed likely, and the diagnostic dilemma was resolved by the reappearance of sugar in the urine one week after discharge from hospital, when aspirin had been discontinued. On re-examination at this time he was found to have glycosuria, a high fasting blood sugar, and a diabeticglucose-tolerance curve (Fig. l). These findings imply that rheumatic fever and diabetes mellitus are in some way incompatible, or that aspirin, the drug used in treatment of acute rheumatism, is anti-diabetic. Earlier reports indicate thatsalicylate was in fact used in the treatment of diabetes and that it prevented glycosuria (Gross and Greenberg, 1948). This information, together with the striking findings in our patient, led us to reinvestigate the effect of aspirin in diabetes mellitus, beginning with mild forms of the disease and, if necessary, progressing to severer types.