Populational aspects of lesser capybara (Hydrochoerus hydrochaeris isthmius) and threaten for the conservation in North-West of Colombia. The purpose of this study was to determine population aspects, threats and the impact of human activi- ties on Lesser Capybara (Hydrochoerus hydrochaeris isthmius) in Department of Cordoba (Colombia). Twenty-eight transects were sampled in order to know the census and geo- graphic distribution. The study area is characterized by flooded alluvial valleys, wetlands, swamps, with a hot climate and yearly dry and rainy seasons. It was found a population of more than 10 000 individuals in Department of Cordoba inhabiting isolated swamps and permanent lagoons. The greatest concentration was found along Rio Sinu with 7995 indi- viduals. The size of the streams, swamps and some permanent lagoons determine the extension of the habitat of Lesser Capybara; however, it depends more on the farmers and administrators attitude, than on the conditions of the habitat. The census of 1272 individuals was based on 103 herds with an average frecuency of 3.83 ±10.69 indiv/Km, with no statistical differences among watersheds (p=0.6905). There were no differences in the size of the herds among watersheds (p=0.0749), with an average of 4.89 ±8.35 indiv/heard. A high index for all the subregions in the Department of Cordoba was found. Threat values