The airborne fungal spore types were studied in different libraries in Delhi, using an Andersen sampler and a Burkard personal sampler, for culturable and non-culturable fungi respectively. The concentration inside the libraries, before and after the agitation of books, were compared with outside air. The major contributors to the library air are Cladosporium, aspergiUi/penicillia, smuts and Alternaria, varying from 50 to 14%. Some fungi (Cladosporium, Alternaria, smut, Penicillium chrysogenum and nigricans) showed seasonal occurrence, corresponding to their occurrence in the extramural environment. Aspergilli/penicillia, Drechslera, Curvularia and Aspergillusflavus had a significantly higher concentration (P < 0.01) inside the library, and recorded a significant increase in concentration after agitation of books. Air-conditioned libraries have low fungal spore concentrations, as compared to naturally ventilated libraries.