Patients with substance abuse problems are common in general medical practice and include people of all ages and socioeconomic groups. Initial diagnosis and treatment of addiction problems are often done by the primary care practitioner before referral to a specialist. This article provides information to help in recognition of addiction, guidelines for treatment of intoxication and withdrawal of various drugs of abuse (such as opioids, sedative-hypnotics, stimulants, hallucinogens, and volatile inhalants), and techniques for brief intervention as well as long-term care of substance-abusing patients. The physician can be a powerful influence for getting the patient to accept treatment, especially when the physician is empathic without being judgmental. Addiction is a chronic disorder with remissions and relapses like any other chronic disease, so exacerbations should not be seen as failures but as time to intensify treatment. Patients with substance abuse problems can be frustrating to treat, but it can also be a rewarding experience when a physician helps a substance-abusing patient return to normal and productive functioning in society.