Objective: To examine the short-term health effects of air pollution on daily mortality in four Australian cities (Brisbane, Melbourne, Perth and Sydney), where more than 50% of Australians reside. Methods: The study used a similar protocol to APHEA2 (Air Pollution and Health: A European Approach) study and derived single-city and pooled estimates. Results: The results derived from the different approaches for the 1996-99 period showed consistent results for different statistical models used. There were significant effects on total mortality, (RR=1.0284 per 1 unit increase in nephelometry [[10.sup.-4].[m.sup.-1]], RR=1.0011 per 1 ppb increase in N[O.sub.2]), and on respiratory mortality (RR=1.0022 per 1ppb increase in [O.sub.3]). No significant differences between cities were found, but the N[O.sub.2] and particle effects may refer to the same impacts. Meta-analyses carried out for three cities yielded estimates for the increase in the daily total number of deaths of 0.2% (-0.8% to 1.2%) for a 10 [micro]g/[m.sup.3] increase in P[M.sub.10] concentration, and 0.9% (-0.7% to 2.5%) for a 10 [micro]g/[m.sup.3] increase in P[M.sub.2.5] concentration. Conclusions: Air pollutants in Australian cities have significant effects on mortality.