Introduction. -- Toward an account of individual differences in drug abuse -- Acquisition and reacquisition (relapse) of drug abuse: modulation by alternative reinforcers -- The influence of behavioral and pharmacological history on the reinforcing effects of cocaine in rhesus monkeys -- Stimulant preexposure sensitizes rats and humans to the rewarding effects of cocaine -- Stress, the hypothalamic-pituitary-adrenal axis, and vulnerability to drug abuse -- Behavioral and biological factors associated with individual vulnerability to psychostimulant abuse -- Addictive behavior with and without pharmacologic action: critical role of stimulus control -- Taste and diet preferences as predictors of drug self-administration -- Individual differences in acute effects of drugs in humans: their relevance to risk for abuse -- Substance abuse vulnerability in offspring of alcohol and drug abusers -- Integrating genetic and behavioral models in the study of substance abuse mechanisms -- Disaggregating the liability for drug abuse.