Background/Aim. In studies that investigate the health effects of short-term air pollution exposure, population-wide changes in acute outcomes such as mortality, hospital admissions and healthcare visits are linked to short-term variations in ambient pollutant concentrations. The aim of this study was to estimate the association between daily outdoor black smoke and sulphur dioxide levels and hospital admissions for cardiovascular and respiratory diseases in Niš, within a period 2001-2005. Methods. A time series analysis was performed using separated regression models for each pollutant and disease group, by age groups and population as a whole. The effects of copollutant, meteorological factors and cyclic oscillations in hospitalization numbers were controlled. Results. A significant increase in hospital admissions was associated with a 10 μg/m3 increase in the concentration of black smoke, for cardiovascular diseases: 3.14% (< 0.01) in children and youth under 19 years of age, 1.85% (< 0.001) in 19-64 age group, and 0.84% (< 0.05) in all ages, and for respiratory diseases: 1.77% (< 0.05) in 19-64 age group, and 0.91% (< 0.05) in all ages. The effects on hospitalizations for respiratory diseases in children and youth under 19 years of age, and for cardiovascular and respiratory diseases in the elderly were not statistically significant. The increase of sulphur dioxide level was associated with the increased number of hospitalizations, for both cardiovascular and respiratory diseases in all age groups, but the influence was not statistically significant. Conclusion. Outdoor pollutants concentrations in urban area of Niš were below regulated limit values during most of the investigated period days but it is shown that even such a level of pollution has a significant effect on hospital admissions for cardiovascular and respiratory diseases.