Article InfoThe control of indoor air quality plays an important role in the prevention of cross infection in hospitals to protect both hospital staff and patients. This study was carried out to determine the variation in microbiota of medical laboratory at Benghazi center infectious diseases and immunity. Samples were collected by using the settled plate techniques for the enumeration of bacterial and fungal isolates. The air specimens were collected through four seasons in the morning between the hours of 9 am and 11 am from air indoor medical lab and swab samples collected from the filters of the air conditioning units in autumn, spring and summer seasons. Indoor air gram positive bacteria, accounting (99.72%) was significantly higher than that of gram negative bacteria (0.28%). The most common bacteria genus found in all seasons were Staphylococcus (46.62%) Micrococcus (27.31%), followed by Kocuria (13.42% ). The most abundant isolated bacteria in the three seasons was Bacillus circulans while Penicillium sp. was the most abundant fungi in air conditioning isolates. In indoor air samples of medical laboratory rooms showed contamination with bacteria and fungi under the acceptable levels, when compared with cited in this study. Indoor airborne bacteria and fungi concentration were depended on place of isolation and seasons.