A bio-aerosol is a suspension of air borne particles that contains living organisms which consists of viruses, bacteria, fungal spores and plant pollens. These tiny particles will stay airborne for longer period and it has harmful effects on environment as well as human beings. The main objective of the present work was to review on composition, sources, modes of transmission, health effects and sampling. This must be used for evaluation of bioaerosols and the selected area. It also supports control measures, to reduce the loads of bioaerosols. The evaluation was conducted in four different houses of the laxmipuram slum area of Bangalore city by using Anderson air sampler instrument.