Among 718 consecutively monitored hospitalized medical patients who received prednisone, adverse reactions were recorded in 121 (16.9 per cent). Of these, 82 experienced acute reactions (11.4 per cent of the total series), and 39 (5.4 per cent) had a more gradual onset of the reactions. The daily dose of prednisone was analyzed in 594 patients in whom adverse reactions were not recorded and in the 82 patients with acute reactions. While there was a striking dose‐response relationship for acute psychiatric reactions, there was no correlation between dose and gastrointestinal side effects, diabetes, superinfections, and leukocytosis.