Publisher Summary The chapter studies drug-induced changes in the cardiovascular system. The recognition of drug-induced structural changes in cardiac tissues in humans is hampered by the problems of differentiating drug-induced injury from a naturally occurring cardiovascular disease. Drug-induced alterations in blood pressure, heart rate, or cardiac conduction in animal studies may have implications for safety of a drug, even if they are devoid of any morphological correlate. In both humans and laboratory animals, the heart weight varies with body weight, body length, age, sex, and other constitutional factors as well as circulatory demands. Findings show that in response to increased demand through a variety of mechanical, hemodynamic, hormonal, or pathological stimuli, the heart adapts by a hypertrophic response. It has also been observed that the fine balance of factors that control myocardial perfusion is emphasized by the observations that adrenergic coronary vasoconstriction as well as vasodilatation occurs during exercise and other forms of generalized sympathetic activation. Cardiac muscle cells can be affected in the generalized form of drug-induced phospholipidosis, which is characterized by the presence of typical lamellate or crystalloid and membrane-bound inclusions.