This Article proposes the catalytic conversion of triglyceride in subcritical water for the purpose of developing a process producing liquid and gaseous fuels without any reagents, such as hydrogen, other than water. The characteristics of the reaction were discussed along with the analysis of the catalytic mechanisms. Pt, Pd, and Ni catalysts supported on carbon were applied to the conversion of a jatropha oil. Pt on activated carbon and homemade Ni on porous carbon catalysts had high enough activities to completely convert the oil into products nearly free from fatty acids at 350 degrees C, but they had distinctly different ways of catalysis, leading to the production of pentadecane/heptadecane and methane, respectively. The hydrogen generated in situ from glycerol by gasification contributed to the increases in the yields of n-alkanes, whereas an unavoidable formation of heavy byproducts, which were undetectable by GC analysis, prevented the jatropha oil from being converted fully into the desired products.