Objective To determine the delta-9-tetrahydrocannabinol (THC) content of cannabis seizures in Egypt. Methods Unheated and heated extracts of cannabis seizures were prepared from the dried flowering tops and leaves (marijuana) or from the resin (hashish) and subjected to analysis using high performance liquid chromatography (HPLC). Results The heated resin extract had the peak of THC in a relative ratio of 31.34%, while extracting the resin directly without heating contained only 18.34% of THC. On the other hand, marijuana showed minimum percentage of THC at 11.188% on heating and 9.55% without heating. Conclusions These results indicate the high potency of the abused cannabis plant in the illicit Egyptian market.