BACKGROUND In 2005, the Sistema de Vigilancia en Salud Pública, the governmental agency responsible for monitoring public health, found that Putumayo Province has the highest incidence of poisoning by pesticides in Colombia. OBJECTIVE Exposure to organophosphorus and carbamate pesticides and carbamates was established in the agricultural population of Putumayo by determining acetylcholinesterase levels. METHODS A cross-sectional survey was made in 204 occupationally exposed workers in four municipalities of Putumayo. A questionnaire was administered to collect subject information; a blood sample was taken for acetylcholinesterase determination by Michels method. A straightforward analysis of the variables and possible associations were explored. A group of workers was enabled with SARAR (a participative educational strategy that means: S: safety, A: association, R: reaction, A: actualization and R: responsability)methodology for use and handling of pesticides. RESULTS The average time of exposure was nine years. Seventy-five percent declared using extremely toxic pesticides and 13% highly toxic. On average, they applied pesticides 7.3 hours/day. Nearly 10% used organochloride pesticides. Furthermore, 17.6% demonstrated inhibition of the enzyme acetylcholinesterase. CONCLUSIONS A realistic scale of the pesticide use problem in humans was obtained; and the data effectively recommend an educatiional intervention for the workers and their families with SARAR methodology.