Shredded scrap automotive tyres were pyrolysed in a static batch reactor in a stream of nitrogen. The products were passed directly to a second heated reactor, where secondary reactions of the pyrolysis vapours occurred. The condensed tyre pyrolysis oil, after secondary reaction, was analysed for the content of polycyclic aromatic hydrocarbons (PAH). The concentration of PAH in the oil was high, reaching over 10% of the total mass of derived oil. Individual PAH of known carcinogenic or mutagenic activity, for example benzo[a]pyrene, benzo[e]pyrene, chrysene and fluoranthene, were present in significant concentrations. The concentration of PAH were found to increase with increasing secondary reaction temperature, the formation of PAH occurring via a Diels-Alder type reaction involving the aromatization of olefinic compounds. The derived tyre pyrolysis oil represents a significant health hazard.