987 hospitalized patients with various cardiovascular diseases were studied for the side effects of the cardiovascular drugs applied. 12 patients (1.2%) were admitted to the hospital because of drug side effects. During the course of hospital treatment 193 types of drug side effects were registered in III patients (11.24%). 128 (66.32%) of the side effects were due to pharmacologic causes, the remaining were of immunologic character. Most of the patients suffering from drug side effects were women--60 (61.4%), and 64.84% of the patients were over 50 years of age. Most of the drug side effects were caused by coronary vasodilating drugs (31.53%), followed by calcium antagonists (18%), cardiac glycosides (12.6%), etc. The need of knowledge of the risks related to the use of cardiovascular drugs as well as the control of the untoward reactions in the course of treatment are pointed out.