The prolonged administration of hydralazine hydrochloride, an antipressor drug, has been found capable of inducing a syndrome that resembles rheumatoid arthritis or systemic lupus erythematosus. In the past it was assumed that, when administration of the drug was discontinued, the "hydralazine syndrome" would disappear permanently. The follow-up study of 11 cases here reported showed that some of the symptoms and findings persisted for years after administration of the drug had been stopped. In four patients the increased erythrocyte sedimentation rate persisted longer than three years; in two it was associated with continued rheumatic pain, and in the other two it was associated with an unchanging hepatosplenomegaly.