A series of 14 new observations of Hyladelphys kalinowskii (Didelphidae) provides novel natural history information about this rare Neotropical opossum, which appears to occur throughout French Guiani (Didelphidae) provides novel natural history information about this rare Neotropical opossum, which appears to occur throughout French Guiana, from highly degraded forest patches of the littoral zone to large tracks of pristine primary forests in the interior. Six nests were found containing one to several individuals, including females with suckling young. It appears that the compo-nents (dry leaves, small twigs) of some nests are glued together with a whitish cement of unknown origin. Includ-ing previously reported records, a total of 18 individuals of H. kalinowskii have now been caught or observed in French Guiana. External and cranial measurements of five adult specimens are tabulated.