The relationship of human brain levels of 3,4-dihydroxyphenylacetic acid (DOPAC) to cerebrospinal fluid levels of this domapine (DA) metabolite was studied. The effect of postmortem delay was evaluated in the rat. DOPAC was resistant to postmortem changes in brain kept in situ. The level of DOPAC (free and conjugated) determined in DA-rich areas of six human brains amounted to only a fraction of the homovanillic acid (HVA) found in the same regions. The DOPAC/HVA ratio in human brain was similar to that found in CSF. We conclude that HVA is the major DA metabolite in human brain and that DA metabolite levels in CSF reflect DA metabolite levels in brain.