The cytochromes P450 are a large family of haemoproteins which have a major role in the oxidative metabolism of a wide range of xenobiotics and some endogenous compounds. In this study the presence of individual members of the CYP1, CYP2 and CYP3 P450 families has been investigated by reverse transcriptase polymerase chain reaction in different regions of normal human brain consisting of frontal and temporal cortices, mid brain, cerebellum, pons and medulla. All the P450s were identified in specific regions of brain with CYP1A1 and CYP2C being the most frequently expressed forms of P450. Sequencing identified the CYP2C PCR product as CYP2C8. This study indicates that individual P450 mRNAs are present in human brain and are found in specific brain regions. The distribution of individual P450s in different regions of human brain is likely to be highly important in determining the response of the brain to toxic foreign compounds.