SummaryTwo severe cases of rheumatoid arthritis were treated by small doses of A. C. T. H.The first patient received a total dosage of 150 mgr in four days and the second 100 mgr in two days; as soon as the first day both improved markedly and the following days the improvement still increased.The swelling of the joints diminished and the pain disappeared completely. The patients were able to get out of their bed and walk without aid.When the treatment was discontinued, injections of insulin I. V. (0,1 unit per Kgr) were performed three times a day in the hope that hypoglycemia, which stimulated adrenal cortex, could prolong the effects of the A. C. T. H.In the 2 patients, the first symptoms of relapse were noted 23 and 25 days after discontinuating A. C. T. H., and the sedimentation rate increased at the same time.Sedimentation rate of erythrocytes, eosinophil count before and after insulin injections, blood sugar and potassium, urinary potassium and chlorids have been determined during the two periods of treatment.We feel that insulin hypoglycemia delayed the relapse and reduced its intensity.