Mature specimens of three catfishes: Capitan de la Sabana ( Eremophilus mutisii ), Bagre Rayado ( Pseudoplatystoma orinocoense and P. metaense ) and Capaz ( Pimelodus grosskopfii ) (n=9-27/species) were sampled in the areas of Bogota River, Puerto Lopez (Meta) and Betania Dam (Huila, Colombia), respectively. Levels of blood lead, plasma cholinesterase (ChE) activity and erythrocytic micronuclei were investigated. Water samples from each location were analyzed for physico-chemical parameters, metals (lead, cadmium, iron and zinc), total petroleum hydrocarbons (TPHs), benzo[a]pyrene, screening test for organophosphates/carbamates and the herbicides glyphosate and atrazine. The main findings in the fish were the presence of lead above 3.3 I¼g/dL in the blood of 93 % of the Capitanes, 44% of the Bagres and 28% of the Capaces, as well as a lower ChE activity in the Capitan as compared to Bagre Rayado and Capaz. No significant numbers of micronuclei were found in any of the species. In the water samples, 7- 14 ppm equivalents of TPHs were found in the Bogota River (Suesca) and 1.5 - 3.5 ppm in the Meta River. Levels of glyphosate (0.5 – 4.0 ppb) were found in the Meta River. The xenobiotic nature of lead makes its presence in the fish an abnormal finding, as is the presence of TPHs and glyphosate in the water samples.