Particle size distribution is important to characterize airborne dust and to design particulate matter control strategies. New data are needed on particle size distribution in swine buildings, and the existing particle size distribution models need to be evaluated. The log-normal, power law, and Weibull models did not adequately describe the particle size distribution of dust samples collected in rooms housing pigs. An alternative two-parameter empirical model was developed that fit the data much more closely than the other models. The parameters of the particle size distribution function did not vary significantly among rooms housing pigs in different stages of production, suggesting that similar dust control strategies may be developed for a wide variety of pig housing facilities.