Fungal basidiospores andCladosporium spores are the two most numerous spore types in the air of Dublin and its surroundings. They are known to have allergenic components, and the aim of the study described here is to develop a predictive model for these spores. A very simple model, which combines an estimated diurnal rhythm with a simple, one-parameter time series model, provided golld short-term forecasts. The one-step prediction error variance was reduced by 88% forCladosporium spores and by 98% for basidiospores.