The objective was to investigate combustion generated PAH in Diesel engine particulate emissions using a pure single component fuel, hexadecane, in a Perkins 4-236 engine in a single cylinder format. The results were compared with those using a conventional Diesel fuel and with the particulates collected by motoring the engine. To minimise any influence of contamination from the PAH in used lubricating oil, all the tests were carried out with fresh PAH free lubricating oil. The hexadecane particulates were found to contain 6-25% of the PAH and 5-9% of the n-alkanes for Diesel and the motoring tests were found to give 10% of the PAH and 50-200% of the n-alkane for hexadecane. It was concluded that there was an internal source of n-alkane and PAH in the engine and exhaust system, probably absorbed in engine deposits. It was therefore not possible to conclude that the PAH with hexadecane was pyrosynthesised.