This paper presents the development, laboratory and field evaluation of two personal particle samplers (PPS). Both samplers operate at a flow rate of 41 min(-1), and collect particles smaller than 1.0 and 2.5 mu m in aerodynamic diameter, respectively, on 3.7 cm Teflon filters. In each sampler, particles larger than 2.5 or 1.0 mu m are retained by impaction onto a coated porous metal disk, which minimizes particle bounce. Using the substrates without any coating results in a substantial reduction of the collection efficiency for particles larger than the 50% cutpoint of the sampler. Particle losses in each sampler are quite low (e.g., on the order of 10% or less) and do not depend significantly on aerodynamic particle diameter. Both samplers display sharp particle cut characteristics, with the ratio of the aerodynamic particle diameter corresponding to 84% collection efficiency to the 50% cutpoint being approximately 1.18 and 1.27 for the PM1 and the PM2.5 samplers, respectively. Field tests showed that the mass, sulfate and nitrate concentrations measured by the PM2.5 PPS and a collocated PM2.5 Personal Exposure Monitor (PEM) agreed within 10% or less. Such agreement, however, was not observed between the PM2.5 PPS and the Harvard/EPA Annular Denuder System (HEADS), with the HEADS nitrate concentrations being on the average higher by a factor of 2.1. The particle mass, sulfate and nitrate concentrations obtained with a modified MOUDI sampler collecting all particles smaller than 1 mu m in aerodynamic diameter on a filter and the PM1 PPS were also in very good agreement (e.,g., within 7% or less). The two personal particle samplers will be used in field studies in different locations of the U.S, to provide better estimates of human exposures to exclusively particles of the accumulation mode. (e.g., without incorporating the contribution of the coarse mode).