A permanent improvement in ambient air quality in the Urban Area of Katowice over recent years could have resulted in a decreased risk of air pollution-related daily mortality. Our study investigates the risk associated with the levels of PM₁₀ and SO₂, obtained seven years apart (time-series analyses in 1994-95 and 2001- 02). For both periods the acute mortality risk depends more on SO₂ than on PM10 levels. The permanent improvement in ambient air pollution was associated with a decrease in relative risk of mortality, only for SO₂ levels. For example, the magnitude of the total mortality relative risk related to a 10 µg/m³ increase in pollutant’s concentration (a 3-day moving average) was for SO₂ 1.019 (1.015-1.023) in 1994-95 and 1.012 (1.005- 1.019) in 2001-02, and for PM10 1.007 (1.004-1.011) in 1994-95 and 1.007 (1.003-1.011) in 2001-02.