Polycyclic aromatic hydrocarbons (PAHs) from ambient air particulate matter (PM) were analysed by a two-step thermal desorption (TD) injection system integrated to a gas chromatograph-mass spectrometer (GC/MS). The operational variables of the TD method were optimised and the analytical expanded uncertainties were calculated to vary from 8% to 16% over the operative concentration range (40-4000 pg). The performance of the TD method was validated by the analysis of a standard reference material and by comparison of PAH concentrations in PM samples to those obtained by a conventional liquid extraction (LE) method. The TD method reported lower uncertainties than the LE method for the analysis of similar concentrations in air. The TD method also showed advantages for shorter sampling times in comparison to 24 h for source apportionment applications and for reducing losses of more reactive compounds such as benzo[a]pyrene.