The effect of p-chloroamphetamine (PCA) on extracellular levels of endogenous 5-hydroxytryptamine (5-HT) and dopamine (DA) in the striatum and frontal cortex of the halothane-anesthetized rat was studied using an intracerebral dialysis method. PCA (5 mg/kg s.c.) induced an immediate, marked release of 5-HT into dialysates collected from the frontal cortex and striatum, an effect which lasted over 2 h. This treatment also caused a marked release of DA in the striatum. The results further emphasize the need to carefully assess the involvement of brain DA as well as 5-HT in PCA-induced behaviors.