The dialysis perfusion method was used to study the effects of haloperidol, electrical brain stimulation, and behavioral activation on extracellular levels of dopamine metabolites in the rat striatum. Systemic administration of 0.2 mg/kg haloperidol increased extracellular levels of the metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) by 2-3-fold. Electrical stimulation of the medial forebrain bundle also increased HVA levels in dialysis perfusates. Rats pressing a lever for food reward showed 10-40% increases in HVA and DOPAC levels that reached a maximum 30-120 min after the behavioral session. The magnitude of the increases in HVA levels were correlated with the number of lever press responses. Presentation of a single 45-mg food pellet every 30 s to food-deprived rats produced a variety of motor activities and also increased the concentration of extracellular HVA. The results of the behavioral experiments indicate that striatal dopamine neurons are activated during conditions that increase motor activity.