Nasal tissues can be exposed to benzo(a)pyrene (BaP), e.g. present in diesel exhaust particles and some workplace atmospheres. In this study rats were given 3H-BaP intranasally. Autoradiography and beta-spectrometry were then used to trace cells in the nasal olfactory mucosa having capacity to activate the compound to tissue-bound metabolites. We also examined if deposition of 3H-BaP on the olfactory mucosa results in translocation of labelled material to the brain along olfactory neurons. The results showed that intranasal administration of 3H-BaP results in formation of tissue-bound metabolites in sustentacular cells and in the cells of Bowman's glands. Initially the bound material was localised to a higher extent to the sustentacular cells than to the cells of Bowman's glands, whereas at longer survival intervals the uptake in the cells of Bowman's glands dominated. In the latter the covalently bound material was accumulated to a higher extent in the nuclei than in the cytoplasms. We speculate that BaP may interact with the aryl hydrocarbon receptor (AhR) in these cells and that AhR may target activated BaP to the nucleus. Our results further indicated that application of 3H-BaP on the nasal mucosa results in transport of BaP and/or BaP-metabolites along the axons of the olfactory neurons to the olfactory bulb.