Summary1°A large increase of the number of patients developing jaundice has been observed among syphilitic patients treated at Brussels St-Pierre Hospital : 30 % of them if treated with neo-arsphenamine developed icterus.2°However this increase of hepatitis cases has also been observed in other kinds of antiluetic treatment.3°Intravenous therapy with trivalent arsenic seemed to produce the highest number of casualties. Bismuth on the contrary gave the lowest increase of the whole series.4°It does not seem that the number of cases is the highest during the third As. cure and rather numerous cases appeared two or three months after As. injections had been stopped.5°Jaundice relapse is not frequent in patients receiving a second cure of As. after recovery of icterus.Authors have also studied the effects of As. therapy on hepatic functional tests. Takata-Ara’s, Hanger’s and Quick’s tests have been used.6°These methods do not help to foreknow those patients who most probably will develop icterus.7°Pathological changes in hepatic tests only appear when jaundice appears or a few days before.8°Hepatic tests have been found normal in several patients with light icterus.Finally pathogenicity of As. jaundice is discussed. Several theories have been proposed. The most probable is that infectious hepatitis develops most easily in patients with a moderate liver damage resulting from arsenical therapy. In some conditions this form of hepatitis has an epidemic character.