Microdialysis of small brain areas of OF1 mice is shown to be feasible using the smallest commercially available probes (CMA/11). The brain areas studied were the dorsal hippocampus and nucleus accumbens. The basal concentrations of biogenic amine metabolites in dialysate samples were measured by HPLC with electrochemical detection (ED). The basal levels of MHPG, DOPAC, and HVA in the dorsal hippocampus were obtained immediately after probe insertion, whereas the basal 5-HIAA concentration gradually declined. The stable levels of DOPAC, HVA, and 5-HIAA in the nucleus accumbens were reached in 80 min. Histological controls showed the tract of the dialysis membrane within the studied sites. This procedure could allow simultaneous correlation of the neurobiochemical changes and pharmacological responses, and could facilitate further biochemical and pharmacokinetic research in the mouse.