Observation of the prompt and pronounced effects of cortisone on rheumatoid arthritis and related diseases has been followed by studies to determine whether specific structural requirements for antirheumatic action could be elucidated. Twelve steroid substances other than cortisone and four adrenal cortex extracts have been administered in twenty-two trials on 11 patients (cases 1 to 11) who had rheumatoid arthritis with and without associated rheumatoid spondylitis. Ten of these 11 patients also received cortisone, pituitary adrenocorticotropic hormone (ACTH) or both. Results of the administration of these substances served as a standard against which the effects of the other preparations were compared. Effects of cortisone (or pituitary adrenocorticotropic hormone) on rheumatoid arthritis have been classified as very marked, marked and moderate.1In this present study a very marked antirheumatic effect is graded as 4, a marked response as 3 plus to 3, a moderate response 2 plus to 2, mild