Size distributions of total airborne particles and bioaerosols were measured in a full-scale composting facility, using an optical particle counter and an agar-inserted six-stage impactor, respectively. Higher concentrations of total airborne particles and bioaerosols were detected at a sampling location near the screening process preceded by the composting process than at sampling locations in the composting process. At the sampling location near the screening process, the concentrations of total airborne particles were approximately 10(8)particles/m3 at the size of 0.3 microm and 10(5)particles/m3 at 6.2 microm. The concentration of bioaerosols was about 10(4)CFU/m3 in each stage of 7.0 microm (1st stage), 7.0-4.7 microm (2nd), 4.7-3.3 microm (3rd), 3.3-2.1 microm (4th), 2.1-1.1 microm (5th) and 1.1-0.65 microm (6th). Most of submicron particles smaller than 1 microm among the total airborne particles were believed to originate from the ambient air.