The kinetics of formation and growth of the nanometer-sized aerosol particles during tungsten hexacarbonyl (W(CO)(6)) vapour photolysis in air have been investigated. Special attention has been given to the research on the influence of coagulation during the time interval (t(1)) between the moment the vapours leave the irradiation zone (i.e, generation of condensing products stops) and the moment particle concentration and size distribution are measured, Aerosol formation kinetics within the Smoluchowski coagulation model in the clusters free-molecular collision regime was modelled numerically. The rate of monomer formation F(t) was calculated for different rates of W(CO)(6) photolysis at various t(1) values. Calculated values of F(t) were in good agreement with measured W(CO)(6) photolysis rates W-phot. Particles concentration and size were shown to be determined by irradiation dose D = I/I-0 x t(0) (I/I-0 is relative irradiation intensity, t(0) is irradiation time), when t(1) >> t(0). (C) 2000 Elsevier Science Ltd. All rights reserved.