The pantanal is one of the world's richest freshwater wetlands. The pantanal is located in the flood plain of the headwaters of the Paraguai river, covering 140,000km². The habitats of the Pantanal are present in a complex mosaic. The major habitat types are: pockets of forests, called capão or cordilheira, seasonally flooded grasslands or campos, and permanent or temporary lagoons, called baías. The Pantanal harbors both rich and abundant mammal fauna. A survey was conducted at Fazenda Nhumirim, a research station run by the Centro de Pesquisa Agropecuária do Pantanal (CPAP) in Corumbá, a research branch of EMBRAPA. The Fazenda covers an area of 4,310 ha in the sub-region of Nhecolândia, appoximately 150km east of Corumbá, Mato Grosso do Sul. The area receives an average annual rainfall of 1,022mm, and has a mean monthly temperature that varies between 29.1ºC (January) and 22.0ºC (June). Four routes were followed between two times during ten days of each month. The survey routes were covered on horseback by between two and four observers. Each route was followed and equal number of times in the morning and in the afternoon, to eliminate bias related to the activity patterns of mammals. In order to evaluate relative abundance of nocturnal species, we also conducted a number of nocturnal censuses. These censuses were done by car; a high intensity searchlight was used to spot the animals. We also conducted a trap-mark-recapture survey of the small mammals at Fazenda Nhumirim. After the census period, we continued to collect observations on the occurrence of mammals at the Fazenda, noting wherever possible the kind of habitat in which the animals were observed. The survey identified a diversity of mammals at Fazenda Nhumirim: six orders, 14 families, 19 genera, and 20 species. Nasua nasua was the most frequently observed species during the diurnal census, accounting for 61.5 percent of all observations. Dusicyon (formely Cerdocyon) thous was the most frequently observed species on the nocturnal census (39.13%). The small mammal community of Fazenda Nhumirim is composed of seven species: one marsupial, four cricetine rodents and two echimyid rodents.