Aims: To assess the microbiological indoor air quality (IAQ) of high school and college gyms during physical training lessons and to evaluate the effective microbiological exposure of students. Methods and Results: Air samples from 11 high school and college gyms of Pavia, Italy were collected. Total bacterial counts, total fungal counts and characterization of fungal taxa were determined. Air quality was evaluated using three microbiological contamination indices: the global index of microbiological contamination per m(3) (GIMC per m(3)), the index of mesophilic bacterial contamination (IMC) and the amplification index (AI). Conclusions: This work testifies that air contamination in indoor gyms is always superior to that of the outdoor environment. Nevertheless, students are exposed to relatively low concentrations of airborne micro-organisms. The highest values of fungal counts and GIMC per m(3) (>14 661) were observed between April and October when the central heating systems were switched off. The lowest fungal counts were detected in modern buildings equipped with forced ventilation systems. From qualitative aeromycological studies, 45 fungal taxa were identified, and different potentially allergenic species were isolated. Significance and Impact of the Study: The standardization of air sampling methods and the correct evaluation of aeromicrobiological results allow the classification of indoor air healthiness. The proposed microbiological contamination indices together with the characterization of airborne fungal taxa are useful tools for detailed description of IAQ.