In a collaborative work, six chemical fractions obtained from smoke of cannabis, prepared by the Department of Biological Chemistry, University of Athens, were assayed pharmacologically at the Department of Psychobiology, Escola Paulista de Medicina, Brazil. The chemical fractions, obtained through burning cannabis mixed with a special tobacco through a water pipe similar to that used by Greek smokers, were: fraction IS composed of water-soluble compounds, fraction IIS made up of water-insoluble substances that condensed at the top of the water phase due to their low solubility; and fraction IIIS, of water-insoluble highly volatile substances, corresponding to the part that reaches the human lungs. Fractions IB, IIB and IIIB were placebo fractions obtained from burning only the special tobacco, called "tubeki", which is mixed with cannabis by the Greek smokers. The six fractions were assayed pharmacologically, in a blind fashion, using the following methods: barbiturate sleeping time in mice, catatonia in mice, corneal reflex in rabbits (Gayer test), and spontaneous motor activity in mice. Fraction IS, and its placebo fraction IB, were inactive in all methods employed, revealing no water-soluble active substances in cannabis. Fraction IIS revealed to be the most active as it induced significant effects in all 4 methods used; its IIB placebo fraction was inactive. Fraction IIIS, composed of the only substances that reach the human lungs, was moderately active; it produced significant effects on barbiturate sleeping time of mice and on the corneal reflex of rabbits, but was inactive in inducing catatonia and in decreasing spontaneous motor activity of mice. These results indicate that devices such as the water pipe used by Greek smokers retain active principles from cannabis.