It has been shown that the heat treatment of pre-ozonized natural bitumen at 340-350 degrees C is accompanied by extensive cracking of the feedstock components owing to the initiation by ozonides of thermal chain degradation reactions. The yield of ibp-350 degrees C fuel distillates from natural bitumen of the Mortuk field (Kazakhstan) after its ozonization and the noted initiated cracking can be brought up to 60 wt.%, which is considerably higher than the potential content of the same fractions in the untreated bitumen (24.2%) and their yield during normal thermal cracking at 450 degrees C (48%). Owing to the lower temperature of the process, ozonide-initiated cracking is accompanied by considerably lower gas and coke formation. The distillates of initiated cracking have a much lower content of sulphur and polycycloaromatic hydrocarbons by comparison with straight-run fractions of untreated bitumen, but, like the products of other thermal degradation processes, contain up to 14 wt.% olefins, can be unstable during storage, and, possibly, require further hydrogenation refining.