Aims: To evaluate a standard aerosolization method for uniformly depositing threat-representative spores onto surfaces. Methods and Results: Lyophilized Bacillus anthracis Delta Sterne spores, coated in silica, were aerosolized into a containment chamber and deposited onto nine surface types by two independent laboratories. Laboratory A produced a mean loading concentration of 1.78 x 10(5) CFU cm(-2); coefficient of variation (CV) was <40% for 96% of samples. Laboratory B produced a mean loading concentration of 7.82 x 10(6) CFU cm(-2); 68% of samples demonstrated CV <40%. Conclusions: This method has been shown to meet the goal of loading threat-representative spores onto surfaces with low variability at concentrations relevant to the Department of Defense. Significance and Impact of the Study: As demonstrated in 2001, a biological attack using anthrax disseminated as a dry powder is a credible threat. This method will provide a means to load spores onto surfaces that mimic a 'real-world' scenario of an aerosolized anthrax attack. The method has utility for evaluating sporicidal technologies and for nondecontamination studies, for example fate and transport or reaerosolization.