A novel method for making cost-effective and reliable size-segregated (15 classes in the range 0.3–20μm) vertical profiles of particulate matter up to 1000m AGL in the planetary boundary layer is described and evaluated. The performance of a commercial miniature particle mass spectrometer is tested against standard gravimetric and optical instruments. The instrument was deployed on a 5m3 kytoon at two sites in the Lower Fraser Valley, British Columbia during the summer of 2001. Results point to significant differences between daytime and nighttime profiles as well as evidence that size distributions in elevated layers have signatures that reflect recirculation of daytime aerosols. Comparisons with lidar observations show good agreement with vertical profiles and indicate that the technique may provide an important aid to interpretation of lidar data.