High density polyethylene (HDPE) thermolysis and polyethylene derived oil hydrogenation were studied as two steps of a novel process to convert waste polyethylene (PE) into a hydrocarbon liquid suitable for use as diesel fuel. This report is focused on the thermolysis of PE. The effects of reaction conditions on reaction rate as well as on the physical and chemical properties of the products were examined. Thermolysis products consisted of liquids (PE oil), polymer residue and gas. The liquid product composition was 80-90 wt. Sc straight chain alkanes and 1-alkenes. Semi-batch reactor thermolysis rates were found to be in good agreement with a theoretical model from the literature. The kinetics of formation of light C-6-C-11, medium C-12-C-16 and heavy C-17-C-20 rr-alkane and I-alkene product fractions from HDPE thermolysis were determined in the temperature range of 400-440 degrees C. Subsequent hydrogenation of the PE oil resulted in a diesel fuel with a high cetane index and low sulphur and aromatic content.