Thermal hydrocracking of n-hexadecane in benzene was carried out in a tubular flow reactor at 400-450 degrees C and total pressure of 13.9 MPa. Hydrogen concentrations in the feed were 2.3 and 2.9 mol %. Mjaor reaction products included biphenyl, C-1 to C-14 n-alkanes, and C-2 to C-15 alpha-olefins. The presence of hydrogen shifted the distribution of n-alkanes toward higher carbon numbers and resulted in a decrease in total molar selectivities for alpha-olefins. Even though a large excess of hydrogen was present, and hydrogenation was thermodynamically favored, selectivities for alpha-olefins were only reduced 5-10%, depending on temperature. Thermal hydrogenation, therefore, was extremely inefficient under the noncatalytic conditions of this study. Unlike thermal cracking of n-C-16 in benzene, product distributions from thermal hydrocracking of n-C-16 in benzene were conversion-dependent. Total selectivities for n-alkanes were in excess of 100 mol per 100 mol n-C-16 decomposed and increased with increasing n-C-16 conversion. Total selectivities for n-olefins were not strongly dependent on n-C-16 conversion. Distributions of alpha-olefins, however, shifted toward lower carbon numbers with increasing n-C-16 conversion. The presence of hydrogen also inhibited the overall conversion of n-C-16 at low n-C-16 conversions (below 3%), but the inhibitory effect disappeared at 5-6% n-C-16 conversion.