In a continuing series of experiments designed to determine the spectral extinction cross-section of bacterial aerosols, a White cell transmissometer was constructed to obtain stable, long path length measurements. Laser transmittance at different aerosol concentrations allows calculation of the extinction cross-sections. Using three lasers, a HeNe at 543 nm, a diode pumped solid state at 1.064 μm, and a fiber laser at 1.558 μm, the data on the spectral cross section of Bacillus globigi (BG) was extended into the NIR. The extinction cross-section was estimated to be 2.58 x 10-8 cm2 at 543 nm wavelength during the 2003 measurements, which is consistent with previous measurements at this wavelength. In the NIR, the cross section of BG was determined to be 2.71 x 10-8 cm2 and 2.32 x 10-8 cm2 at 1.064 and 1.558 μm, respectively. To validate the measurements, Mie calculations were used to continuously represent the extinction and backscatter cross-sections from the UV to NIR. The efforts described herein are intended to explore the various optical scatter features that may allow discrimination of biological pathogens from naturally occurring aerosol constituents such as pollen, dust, etc.