AIM The aim of this study is to estimate the influence of high levels of air pollution during intrauterine development and early childhood on the respiratory functions at a later stage in life. MATERIAL AND METHODS The subjects were children from Dimitrovgrad - one of the most industrialized areas in Bulgaria. The transition to market economy (after 1989) was accompanied by a great drop in industrial production and levels of air pollutants respectively. A complete functional respiratory test of 122 clinically healthy ten-year-old children (48 boys and 74 girls) from Dimitrovgrad was carried out (MasterScreen Diffusion, Jaeger, Wuerzburg, Germany). The participants were distributed in 3 groups: First group (I), n=60 - born and lived to their fifth year of age under conditions of heavy air pollution, and whose mothers had their pregnancies in the same environment; Second group (II), n=39 - born and lived after the abrupt production drop, under considerably lower level of pollution, but whose mothers had their pregnancies prior to that; Third group (III), n=23 - born after the abrupt production drop, lived in conditions of considerably lower level of pollution, and whose mothers had their pregnancies in this more favorable environment. RESULTS The lowest functional indicators of external breathing in the children from the first group were found. FEV(1%pred) - 100.41+/-12.05 (I), 107.38+/-12.55 (II), 111.56+/-11.08 (III), P(IvsII)=0.017, P(IvsIII)=0.001, P(IIvsIII)=0.57; TLC(%pred) - 89.85+/-8.54 (I), 102.76+/-11.57 (II), 102.83+/-11.47 (III), P(IvsII)<0.0001, P(IvsIII)<0.0001, P(IIvsIII)=1. CONCLUSION The research makes an attempt to provide evidence for the negative influence of high levels of air pollution during the intrauterine development and during early childhood, manifested by respiratory limitations at a later stage of childhood. It is known that the influence of air pollution with TSPM and SO(2) during the first 5 years of life is more important than that in intrauterine development for the respiratory functions. Data is lacking with concern to intrauterine programing of respiratory function. Further research is necessary for a detailed elucidation of the problem.