The pharmacology of most addictive substances is being studied extensively, not just for their acute effects but also the mechanisms that lead to drug seeking and addiction. The understanding of how these drugs alter their effects at the molecular level with continuing use gives promise toward investigation of novel substances that may be used for treatment. Genetic predisposition and gender differences are also some of the areas where more research is needed. Women who are addicted are likely to continue drug use during pregnancy, which can have an impact on the next generation. Prevention measures at the population level are as important. Programs need to address risks, social issues, and environmental factors that promote drug use and addiction.