Instrumentation, consisting of a Shuttle Particle Sampler (SPS) and a Shuttle Particle Monitor (SPM), has been developed to characterize the airborne particulate matter in the Space Shuttle cabin during orbital flight. The SPS size selectively collects particles in four size fractions (0-2.5, 2.5-10, 10-100, and >100 μm) which are analyzed postflight for mass concentration and size distribution, for elemental composition, and for morphology. The SPM provides a continuous record of particle concentration through photometric light scattering.Measurements were performed onboard Columbia, OV-102, during the flight of STS-32 in January 1990. No significant changes were observed in the particle mass concentration, size distribution or chemical composition in samples collected during flightday 2 and flightday 7. The total mass concentration was 56 μg/m3 with approximately half of the particles larger than 100 μm. Elemental analysis showed that roughly 70% of the particles larger than 2.5 μm were carbonaceous with small amounts of other elements present. The SPM showed no temporal or spatial variation in particle mass concentration during the mission.