Portable microbial samplers are being increasingly used to determine the presence of microbial agents in the air; however, their performance characteristics when sampling airborne biological agents are largely unknown. In addition, it is unknown whether these samplers could be used to assess microbial inhalation exposure according to the particle sampling conventions. This research analyzed collection efficiencies of MAS-100, Microflow, SMA MicroPortable, Millipore Air Tester, SAS Super 180, BioCulture, and RCS High Flow portable microbial samplers when sampling six bacterial and fungal species ranging from 0.61 to 3.14 microm in aerodynamic diameter. The efficiencies with which airborne microorganisms were deposited on samplers' collection medium were compared to the particle inhalation and lung deposition convention curves. When sampling fungi, RCS High Flow and SAS Super 180 deposited 80%-90% of airborne spores on agar - highest among investigated samplers. Other samplers showed collection efficiencies of 10%-60%. When collecting bacteria, RCS High Flow and MAS-100 collected 20%-30%, whereas other samplers collected less than 10% of these bioparticles. Comparison of samplers' collection efficiencies with particle inhalation convention curves showed that RCS High Flow and SAS Super 180 could be used to assess inhalation exposure to particles larger than 2.5 microm, such as fungal spores. Performance of RCS High Flow sampler was also reflective of the particle lung deposition pattern when sampling both bacteria and fungi. MAS-100 and SAS Super 180 matched the total deposition curve fairly well when collecting bacterial and fungi species, respectively. For other tested samplers, we observed substantial discrepancies between their performances and particle deposition efficiencies in the lung. The results show that feasibility of applying portable microbial samplers for exposure assessment depends on a particular sampler model and microbial species.