Fluctuations of cortical dopamine during feeding were examined by in vivo microdialysis. Dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were measured by high performance liquid chromatography and electrochemical detection. Food-deprived rats were trained to eat by pressing a bar for food when a light and a feeder were turned on. The day of the experiment a microdialysis probe was inserted in the prefrontal cortex (PFC) of the rats and dialysates were collected every 20 minutes while the light and the feeder were off. When the neurochemical baseline was stable the light and the feeder were turned on for 20 minutes only. During this time the rats ate (mean 204 pellets = 9.2 g) and DA increased about 55%, remained high for another 20 minutes and then gradually returned toward baseline levels. DOPAC increased 30% in the first 20 minutes after the eating bout. HVA increased 40 minutes after the eating bout. Histology showed the probes were located in the anteromedial region of the PFC. We conclude that dopamine turnover in the mesocortical system increases during feeding under the conditions used. The results are discussed in terms of the role of the PFC in food intake modulation.