Flame spreading from 0.5 to 2.25-inch V-gutter baffles in two-dimensional turbulent ducted flow was studied experimentally. Measurements of combust ion efficiency were made at distances of 10 to 43 inches downstream of the flame stabilizing baffle(s) in a 9 X 5-inch duct . The effects on efficiency of several geometric and operating variables were observed. Little effect of baffle size was noted, but efficiency increased when reducing the spacing between baffles (or between baffle and wall) by adding more baffles. Pressure dependence was variable. Efficiency increased wi th pressure (over the range of Vs to /3 a t m abs tested) when using geometries giving h igh flame spreading rates, but there was l i t t le change when using geometries giving low rates. Smaller effects were found on changing equivalence ratio (faster burning occurred nearer stoichiometric mixtures) and velocity (efficiency decreased when velocity increased). Miscellaneous data are noted for changes in tailpipe l ength , fuel vaporization, and nature of turbulence. An empirical correlation is presented which groups together in a s imple way m o s t of the data taken. Many variables interact complexly in flame spreading and no accurate s imple description seems likely. Thus , neither the concept of a wrinkled laminar flame, nor of an extended reaction zone, nor of homogeneous combust ion fits the data generally—although any one concept may be acceptable over a restricted range. Burning is probably discontinuous in microt ime making inapplicable theories assuming cont inuous burning.