A study on the distribution of isoprenoid structures in the five fractions obtained by mild Na2Cr2O7/AcOH stepwise oxidation of Green River kerogen is presented. Gas chromatography-mass spectrometry analysis of the fractions resulted in the identification of a homologous series of isoprenoid acids ranging from C14-C21with C16as the largest and C18entirely absent, as well as the two isoprenoidal ketones: 6,l0-dimethyl-2-undecanone and 6,10,l4-trimethyl-2-pentadecanone. A semiquantitative analysis of these components was performed using an INCOS 2300 data system. On the basis of the results obtained, it is suggested that isoprenoid structures do not constitute more than 4% of the kerogen matrix. The results also substantiate previous assumptions that the phytol side chain of chlorophyll is the most likely pre-genitor to the chain isoprenoids found in Green River kerogen.