Topographical variations in the endogenous content of dopamine were studied in the rat caudate-putamen. For this purpose, a high performance liquid chromatography with electrochemical detection procedure for the determination of norepinephrine, epinephrine and dopamine in nervous tissue samples is described. Tissue preparation required only homogenization in acidic solution and centrifugation prior to application to the chromatograph. Detection limits in the low picogram range were found for the catecholamines separated. This assay was used in combination with a micropunch dissection technique. The performance of this analytical technique is illustrated by the detailed mapping of dopamine content in 35 subregions of the rat caudate-putamen. The distribution of dopamine varies along the major axis of the nucleus.