Associations found in time-series studies on hospital emergency room (ER) visits due to asthma and chronic obstructive pulmonary disease (COPD) with single air pollutants show some lack of consistency. The respiratory effects of aeroallergens in the air pollution mix are not well established. Non-linear relationships of different airborne pollen types with certain respiratory diseases have also been described. We aim to study the short-term effects of major air pollutants and aeroallergen pollen on asthma and COPD hospital ER visits in the industrial and Mediterranean Spanish city of Cartagena during 1995-1998.The association of asthma and COPD to ER visits with mean levels of sulphur and nitrogen dioxides (SO(2) and NO(2)), total suspended particles (TSP), ozone (O(3)), and the main allergenic airborne pollen types were analysed using Poisson regression with Generalised Additive Models, taking into account delayed effects and adjusting for long-term trends, seasonality, weather conditions, holidays and flu notifications.Multipollutant models showed a similar relative risk (RR) increase (in %), of around 5% in asthma and COPD ER visits per 10 μg/m(3) SO(2) increments. The risk of an ER visit for the same NO(2) increment was 2.6% for asthma and 3.3% for COPD. Visits to the ER due to asthma showed a positive increase with both Urticaceae and Poaceae levels, but did not substantially modify the previous percentages.Air levels of SO(2) and NO(2) were associated with a substantial increased risk in ER visits due to asthma and COPD. The inclusion of Poaceae and Urticaceae pollen did not alter that association.