This paper describes the reactivity of premixed propylene/air mixtures co-flowing around a flat, vertical, unconfined, rectangular, platinum plate. Measurements and detailed computational fluid dynamics (CFD) calculations are performed to study the effects of varying the temperature of the incoming mixture (T-jet), its equivalence ratio (Phi) and the Reynolds number (Re), on the reactivity limits, platinum surface temperature and species distributions adjacent to the plate. A detailed surface chemical mechanism is implemented in the CFD calculations while pyrometry and gas chromatography are used, respectively, for surface temperature measurements and gas analysis. It is found that the platinum plate temperature peaks at slightly rich propylene/air mixtures (Phi = 1.3) when flameless combustion (defined by the presence of reactions on the plate without a gaseous flame) is observed. While the lean reactivity limits over platinum are lower than those for gaseous propylene/air mixtures, the rich limits are also lower than those of the gas phase alone and a sharp drop in the surface temperature is observed at Phi = 1.4. This sharp transition to extinction may be due to surface contamination by soot precursors. Carbon monoxide (CO), and hydrogen (H-2) appear in low quantities at certain flow conditions. Consistent with other fuels, the streamwise profiles of species confirm the presence of two reacting zones along the plate, namely: (i) the leading edge zone where high gradients of species mole fractions are observed and (ii) the trailing zone where the profiles are more flat and stable. Numerical simulations show broad agreement with measurements up to Phi = 1.4 but fail to reproduce the sharp transition to extinction hence overpredicting the rich reactive limits. Major species such as O-2, C3H6, and CO2 are in good agreement with the measured mole fractions while some discrepancies are noted for CO and H-2. Differential molecular as well as thermal diffusions are found to be significant hence disrupting the atomic balance and leading to leaner mixtures in the vicinity of the plate. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.