An earlier study evaluated the physical performance of the Swirling Aerosol Collector, also known as the ''BioSampler,'' and found it to have several advantages over the widely used AGI-30 impinger when tested with inert test particles. The present study was focused on the physical and biological performance with laboratory-aerosolized micro-organisms. The results showed that the BioSampler has better physical collection efficiency for B. subtilis and P. fluorescens than the AGI-30 when water was used as the collection fluid and the sampling flow rate ranged from 8.5 L min-1 to the standard 12.5 L min-1. Additionally, the BioSampler provided equivalent or better microbial recovery for the 2 species than the AGI-30 did. The swirling motion of the collection liquid in the BioSampler generates very few bubbles and therefore causes minimal reen trainment of already collected micro-organisms. In contrast to the AGI-30, the BioSampler can be used very effectively with nonevaporating liquids, such as mineral oil or glycerol. Mineral oil was found to be a suitable collection fluid for culture analysis, whereas glycerol can be used only for nonculture assays, such as the polymerase chain reaction. By using a more viscous, nonevaporating fluid, the BioSampler can be used for long-term sampling of low airborne bacterial concentrations, while the AGI-30 impinger, filled with a standard evaporating fluid, can only be used for up to about 30 min.