In research carried out in 1982, which included the cultivation of cannabis plants with low, medium and high levels of Δ 9-tetrahydrocannabinol (THC), the authors have determined the parameters for individualization and classification of cannabis plants according to their intoxicant potential. This can help to provide courts of law with valid supportive expertise on cannabis trafficking cases. The parameters are the percentages of THC in cannabinoids and in the dried substance of a plant, as well as the percentage of cannabinoids in the dried substance. On the basis of these parameters, the authors have found that a cannabis plant in which the percentage of THC exceeds 50 per cent of the total amount of cannabinoids of the extractable resin and 0.3 per cent of the total amount of dried substance, and in which the amounts of resin and cannabinoids are substantial, has a considerable intoxicant potential and is liable to be used for illicit production of cannabis for abuse. On the contrary, a plant with a THC level below 50 per cent of the cannabinoids and 0.3 per cent of the dried substance, in addition to a low level of total cannabinoids, has low intoxicant potential and can be used in industry for the production of oil and rope. On the basis of these parameters it is also possible to predict the intoxicant potential of a young cannabis plant harvested at a relatively early stage of its development.