Abstract : Phase 1 of the Defense Special Weapons Agency (DSWA) Transport and Dispersion Model Validation test was conducted in September 1996 at the U.S. Army Dugway Proving Ground Photo Pad 2 test site to acquire a puff ensemble database for validation of next generation puff dispersion models, specifically the Second Order Closure Integrated Puff (SCIPUFF) model. The test consisted of a series of tracer (propylene) puff releases into the atmosphere at distances ranging from 200 to 1200 m upwind of photoionization detectors (PIDs). The PIDs sampled the puff as it passed through the detector line, providing tracer gas concentration measurements. A total of 32 trials were completed. Puff data from these trials have been consolidated into ensembles in the relative (puff centered) frame of reference for use in validating the probabilistic prediction capabilities of SCIPUFF and other next generation models.