The aim of this study was to investigate the effects of occupational exposure to 1,6-hexamethylene diisocyanate (HDI) on peak flowmetry in automobile body paint shop workers in Iran. We studied a population of 43 car painters exposed to HDI at their workplaces. Peak expiratory flow was tested for one working week, from the start to the end of each shift. Air was sampled and HDI analysed in parallel, according to the OSHA 42 method.Daily and weekly HDI exposure averages were (0.42±0.1) mg m -3 and (0.13±0.05) mg m -3 , respectively.On painting days, 72 % of workers showed more than a 10 % variation in peak expiratory flow. Inhalation exposure exceeded the threshold limit value (TLV) ten times over. This strongly suggests that HDI affected the peak flowmetry in the studied workers. Cilj je ovog ispitivanja bio utvrditi vršni protok u 43 iranska autolakirera profesionalno izložena 1,6-heksametilen diizocijanatu (HDI). Vršni ekspiratorni protok testiran je tjedan dana na po _etku i kraju svake smjene. Uzorkovanje i mjerenje HDI-ja u zraku radilo se istodobno s testiranjem vršnoga protoka, prema metodi OSHA 42.Prosje _na dnevna izloženost radnika HDI-ju iznosila je (0.42±0.1) mg m-3, a tjedna (0.13±0.05) mg m -3 . U 72 % radnika vršni ekspiratorni protok tijekom dana varirao je više od 10 %.Radnici su udisali deset puta više razine HDI-ja od grani _nih te je moguće da je HDI utjecao na mjerenja plućne funkcije.