The metabolic activation of numerous exogenous and endogenous chemicals is catalysed by cytochrome P450 enzymes (CYPs). The aim of this study was to analyse the expression of the individual forms of CYP at the mRNA level in human larynx and quantitatively to compare their expressions in human liver, the main in organ of CYP expression. Individual forms of CYP mRNAs were detected by reverse transcriptase-polymerase chain reaction (RT-PCR) using specific primers for the CYPs -1A1, -1A2, -2A6,-2B6,-2C, -2D6, -2E1, -3A3/4 ,-3A5, -3A7 and 4B1. An RNA competitor of known copy number, covering the primer sequences necessary to amplify the entire object CYPs within a single molecule, was used as reference. This study reports a consistent detection of mRNAs for the CYPs -1A1, -2A6, -2B6, -2C, -2D6, -2E1, -3A5 and -4B1 in the human larynx tissue. The data indicate that the human larynx highly resembles the lung tissue in CYP content, as a comparable subset of CYP mRNAs was detected in the larynx previously reported for human lung with the exception of CYP1A2. The results are discussed in quantitative ratios of the detected CYP mRNAs in relation to the hepatic CYP expression. Copyright (c) 2006 John Wiley & Sons, Ltd.