In this study, concentration and size distribution of bioaerosols (bacteria and fungi) were obtained in indoor at minimum ventilation and during the operation of air condition system (ACS). Indoo/Outdoor concentration ratio (I/O) of bacteria and fungi were also determined. In addition, the indoor exposure dose (IED) of bacteria and fungi were calculated. A six-stage Andersen cascade impactor was used for sampling the microorganisms during summer season at Minia University, El-Minia (Egypt). Mean bacterial and fungal concentrations were higher (727±160 and 252±60 CFU/m3, respectively ) at minimum ventilation than the concentrations during ACS (506±120 and 176±44 CFU/m3, respectively ). Indoor bacterial concentration level is three times higher than the fungal level. On the other hand, outdoor bacterial concentration (220±55 CFU/m3) is lower than the outdoor fungal level (300±77 CFU/m3). I/O concentration ratio of bacteria was greater than unity indicating that the main source of bacteria is the human occupancy while the corresponding I/O concentration ratio of fungi was less than unity indicating that the fungi are released from outdoor sources. Mean IED of bacteria (38.5 CFU/kg) was about three times higher than the IED of fungi (13.4 CFU/kg) .