Two prototype high flow dichotomous samplers, each simultaneously collecting fine (0.0-2.5 micrometers), coarse (2.5-10.0 micrometers), and total (0.0-10.0 micrometers) particle samples from a single air stream, have been designed and evaluated. A series of tests were conducted to estimate the prototype sampler collection efficiencies over a range of particle concentrations, to compare prototype sampler collection efficiencies with standard particle monitors, and to evaluate relationships between particle size and sample chemistry. No statistical differences in particle collection efficiencies were observed between the two prototype samplers or between the prototype samplers and standard PM(10) and PM(2.5) high volume samplers. The study analytical results indicate that the particle bound organics are primarily associated with the fine particle sample and that the organics associated with the coarse particle fraction did not significantly contribute to the total sample organic composition. The prototype sampler can be constructed locally from routine sampler and machine shop components. The design minimizes the extensive resource requirements associated with low flow dichotomous sampling and is an excellent alternative for organizations not having access to commercial low flow dichotomous instrumentation. (Copyright (c) 1990 Pergamon Press plc.)