The Atlantic Forest small mammal land fauna, except bats, and the abiotic factors that might have an influence on its composition, were studied in the Itapevi County, State of Sao Paulo, a forested region, partly altered by antropic action, from January, 1995 to June, 1996. The trapping effort consisted of 2,888 trap-nights, resulting in a 4.6% trapping success and consisted of monthly trappings, for five consecutive days. During this period, 134 specimens were captured, of which 46.3% were Didelphimorphia and 53.7% were Rodentia. Eleven species were registered: two Didelphimorphia: Didelphis marsupialis (Linnaeus, 1758) and Marmosops incanus (Lund, 1841), and nine Rodentia: Akodon cursor (Winge, 1887), Bolomys lasiurus (Lund, 1841), Oxymycterus hispidus Pictet, 1843, Oxymycterus nasutus (Waterhouse, 1837), Oligoryzomys nigripes (Olfers, 1818), Oryzomys angouya (Fischer, 1814), Raltus norvegicus (Berkenhout, 1769), Euryzygomatomys spinosus (G. Fischer, 1814) and Cavia aperea Erxleben, 1777. The relative density indices were correlated with meteorological data by Spearman and Pearson coefficients. For marsupials these correlations were not significant. For rodents, the correlations were significant and directly related to lower temperature and rainfall indices (p<0.05). During the dry season the occurrence of small mammals was 50% greater than during the wet season, probably due to foraging strategies in the studied fragment of Atlantic Forest.