DURING the past decade the trend in the therapy of rheumatoid arthritis has been toward the use of hormones. Estrogenic substances, testosterone, pregnenolone, desoxycorticosterone acetate, cortisone, and corticotropin have been used with varying degrees of success and failure. Cortisone and corticotropin are the two most recent additions to the armamentarium. However, they have many significant limitations and contraindications, as reported in the literature by Davison1 and others. Because of these drawbacks to their universal use, the search for other active hormonal agents continues. Since 1950 I have been using placental blood serum in the therapy of rheumatoid arthritis to evaluate its antirheumatic activity, toxicity, and side-effects.In 1938, P. S. Hench2 reviewed the literature for observations of the ameliorating effect of pregnancy on rheumatoid arthritis. He found, from 1864 onward, 10 authors giving accounts of 37 cases of pregnancy among 20 women suffering with active rheumatoid arthritis.