During a seven-month field investigation among a group of Yebamasa indians on the middle Piraparana, Comisarla del Vaupes, Colombia , the author has collected data about the cultural dimension or context of the consumption of the hallucinogenic drink "caji", which most probably is made of various Banisteriopsis spp .. His initial hypothesis is that the individual drug experience is patterned and standardized by learning processes and by the ceremonial circumstances of the consumption of the drug "Caji" is for the Yebamasa a vehicle of spiritual qualification. Every male- Yebamasa strives for higher spiritual rajnking, i.e. he wants to be a "kumu". a shaman. To reach his aim he must again and again drink caji and hope to produce the correct and desired reactions. The criteria for these reactions, both physically and psychically, are set up and defined by the experienced men, above all the higher rallking shamans. Thus there is, indeed, littIe space left for individual variations of established patterns, the more so as the drug is never taken outside religious feasts and outside the context of collective action . Yet, the author has to modify his hypothesis: he underestimated the influence of individual psychic disposition: anxieties. hopes and aspirations rooted in a man's life history which may considerably condition the basic character of a man's experiences. The author holds that most everything connected with the drug is part and parcel of a general and comprehensiVe design for effective control of the drug effect and he is convinced that elements of this system of social control of drug con­sumation, which has enabled the indians to integrate a strong hallucinogenic drug into their culture and live with it for millennia, may well be used in the control of drug addicts in industrialized societies. He consequently has submitted his proposals to the Colombian National Board of Narcotics and plans to submit a simiar paper to the West-German Ministry of Youth, Family, and Health in due time.