An extensive survey of the indoor airborne fungal flora of various working environments was carried out in the Calcutta metropolis for three years (June 1980 to July 1983). Nineteen fungal forms from nine genera were trapped by using Rotorod sampler and exposure culture plate method, then isolated and identified. Spores ofAspergilluswere found to occur in highest frequency in all indoor environments, followed byHelminthosporium, Alternaria, Curvularia, Penicillium, Rhizopus, CladosponumandCandida. The relative concentration ofAspergilluswas maximum during the post-monsoon period and minimum during the winter season. All the trapped fungal forms have been proved to be pathogenic and also allergenically potent.