There is a vast array of abused drugs, and only a few of the more commonly used substances have been discussed. Patients with drug abuse frequently present with atypical syndromes and diseases. These individuals usually have less social, medical and economic support, making them more susceptible to the diseases that are associated with poverty, such as tuberculosis, and the complications of diseases such as hypertension, congestive heart disease and diabetes that require long-term care. Our strategy in the evaluation of these patients should consider all these aspects of medicine. A meticulous assessment and comprehensive care are necessary to render quality care for these complicated human and toxicological problems.