A long-term (1970-1994) study of atmospheric aerosol has been conducted in Kitakyushu City. The annual mean concentrations of aerosol had gradually decreased until 1983 and they have been stable since then. To investigate the change of the aerosol quality, the total mass and constituents of aerosols collected for 1972-1974 (period I : heavily polluted period) and 1984-1988 (period II : improved period) were compared. The decrease rate (%) of all constituents (inorganic ions : SO42-, NO3-, F-, Cl-, Ca2+ and Mg2+ ; metals : Fe, Mn, Zn, V and Pb) except SO42- was much larger than that of the aerosol amount. The concentration of NO3- in the aerosol in period II was 54% of that in period I. It was considered that this result was based on the decrease (period II/period I : 45%) of atmospheric NOx, which was supposed to be a precursor. In contrast, there was a nonproportional relationship between the decrease (88%) of SO42- in the aerosol and the decrease (20%) of atmospheric SO2. These results show the characteristic of the change of aerozol in Kitakyushu City for 24 years (1970-1994).