BACKGROUND Olea europaea pollen is one of the most abundant constituent pollens in Seville (southern Spain). It is responsible for many documented cases of pollinosis in the area. OBJECTIVE To contribute to the useful knowledge of Olea europaea for allergists. METHODS The number of Olea europaea pollen grains in the atmosphere was recorded during 8 consecutive years (1987-1994), using a Cour collector. RESULTS The concentration of Olea europaea pollen was as high as 250 to 1015 grains/m3 only during 1 or 2 weeks in April and May. Overall annual production of O. europaea pollen alternated between years. The beginning of the main pollination period was related to the mean temperature of the preceding months (February and March). Pollination occurred when the mean temperature in both months was higher than 14 degrees C; conversely it was delayed when the mean temperature was lower. Main pollination period length depended upon both temperature and rainfall during this period: temperatures higher than 19.5 degrees C and absence of rainfall shortened the main pollination period, while lower temperatures (15 to 18 degrees C) together with rainfall rates above 100 mm lengthened it. CONCLUSIONS Climatic variables such as preceding mean temperature and rainfall impact on pollen anthesis of Olea europaea affect onset and duration of pollination. A consideration of yearly cycles of pollen production as well as these variables should allow pollen forecasting.