Nondestructive neutron activation analysis employing reactor neutrons and a Ge(Li) gamma-spectrometer has been used to determine the trace element level of air particulates in various areas of Hong Kong. Comparison of the average concentrations of the trace elements of air particulates was made among industrial, heavy-traffic and residential areas. It was found that industrial areas have higher concentrations of Co, Cr, Hg, Mn and Zn, while heavy-traffic areas have very high concentrations of Br. Comparison of the pollution level of Hong Kong with other cities was also made. The average concentrations of Co, Cr, Hg, Zn and Br of air particulates in Hong Kong were found to have higher values than those of other cities. Finally, daily variation of the trace element level in a special area (Hung Hom) had been studied, but no significant variation was found. © 1979 Akadémiai Kiadó.