Airborne pollen in Ulmus and Cupressaceae taxa are im- portant early spring allergens in North America. Various climate factors and global warming may affect pollen release and magnitude, and there- fore have important consequences for sensitive individuals. METHODS: Airborne pollen was collected since December 1986 with a Burkard Spore Trap located on the roof of a building at the University of Tulsa. Burkard slides were prepared and analyzed using standard proto- cols, and daily concentrations were obtained. The data was analyzed for seasonal trends and also correlated with meteorological data. RESULTS: Over 20 years, cumulative season total (CST) increased for Cupressaceae pollen (r50.61, p<0.005), paralleling the increase in red ce- dar trees in Oklahoma. CST for Ulmus pollen showed little change despite declining elm populations. Season start dates occurred earlier over time for both taxa but results were insignificant. Start date, peak, and season length showed considerable variation. Pollen concentration showed significant, positive correlations with daily maximum, mean, and minimum tempera- tures, but the strongest correlation occurred with maximum temperatures for both Ulmus (r50.49, p<0.001) and Cupressaceae (r50.60, p<0.001). Pollen concentration showed significant, negative correlations with precip- itation on that day and on the previous two days. The strongest correlation occurred with previous day precipitation for both Ulmus (r5-0.18, p<0.001) and Cupressaceae (r5-0.33, p<0.001). Preseason weather also showed significant correlations with pollen parameters. CONCLUSIONS: Global warming has no direct effect on pollen release but may be partially responsible for the increase in Cupressaceae pollen. Temperature and precipitation are effective indicators of pollen magnitude and preseason predictors of pollen release.