Demographic studies on small mammals were carried out in the Biological Reserve Carpanta, in the eastern cordillera of the Colombian Andes, at 3000 m of altitude. The capture‐recapture method was used in a 1.2 ha grid with high Andean forest and paramo vegetation, between February and March of 1989. Eleven species of rodents, insectivores, marsupials and carnivores were captured and other three species were reported for the zone. It seems that demographic parameters are influenced by the season of highest precipitation. Diets, preference of habitats and home range are also discussed.