The combustion behavior of a cylindrical port burning polyvinyl chloride plastisol hybrid fuel grain in an oxidizing stream of gaseous oxygen has been studied. The effect of aluminum metal powder on the regression of the hybrid fuel has been investigated over a wide range of loading from 2 to 45% at varying oxidizer flow rates and combustion chamber pressures. The regression rates have been found to be higher for aluminized fuels; however, increasing metal loading has been found to yield decreasing regression rates. An empirical relationship has been obtained between the metal loading and the regression rate of the fuel. The average regression rate and mass consumption rate of the fuel have been correlated with the oxidizer flow rate and initial oxidizer mass flux. Nomenclature A,B,C — empirical constants dj = throat diameter of the nozzle, mm dp = port diameter of the fuel grain, mm G = total mass flux, g/cm2s Goi = initial oxidizer mass flux, g/cm 2s L = length of the fuel grain, cm M =mass fraction of the aluminum metal in the aluminized plastisol Mmax =mass fraction of the aluminum metal in the aluminized plastisol at which the regression rate is maximum mf = rate of fuel mass consumption, g/s m0 = rate of oxidizer mass flow, g/s n = exponent pc = combustion chamber pressure, kg/cm 2 Pj = injection pressure, kg/cm2 f = average fuel regression rate, mm/s