Abstract: 1. The oil from fruits of Chinese drug,"Ya-tan-tze", Brucea javanica(Linn.) Merr., has been studied, and its physical and chemical constants determined. The composition of fatty acids and unsaponifiable matter were also individually identified. 2. The composition of fatty acids was fractionated by a specially modified method of fractional precipitation with silver nitrate solution, while the unsaturated fatty acids were fractionated with bromo-derivative method. The percentage contents of the various fatty acids present are as follows: (1) Saturated fatty acids: Arachidic acid......66.94% Unknown acid......30.09% Caproic acid......2.96% (2) Unsaturated fatty acids: Oleic acid......99.25% Linolenic acid......0.75% Clupanodonic acid......trace 3. From the unsaponifiable matter fraction, a higher homologue of hydrocarbon was isolated. It is a kind of colourless flake crystal, m.p. 61-63℃, its formula being proposed as C₃₅H₇₂ by molecular weight(Rast method) determination. This hydrocarbon is thus preliminarily proved as an isomer of pentatriacontane, a new constituent in this genus of the plant, although the isolation of another hydrocarbon, hentriacontane, C₃₁He₆₄, from the fruits of Brucea sumatrana Roxb. had been previously reported. Besides the hydrocarbon, a trace of phytosterol was also found in the unsaponifiable matter, its acetylated product, a kind of colourless thin flake crystal, m.p. 104-106℃, admixed with a trace of paraffin wax.