Cotton rats (Sigmodon hispidus) invaded sand pine scrub in central Florida in 1974. One episode of dispersal was observed in January–March and a second commenced in May and ceased in November. Invasion was not observed on three study grids during 1973, 1975, or 1976. Small numbers of immigrant cotton rats settled on the grids during 1974 and breeding took place; however, 60% of the individuals tagged and released were not recaptured. These latter animals were presumed to have continued to disperse. Supplemental food on one of the study grids did not prevent the decline of cotton rats in 1974. The sand pine scrub appeared to have acted as a dispersal sink for cotton rats which underwent dispersal from more optimal habitat in surrounding pine flatwoods. Dispersing animals were healthy, equally divided between the sexes, and included all weight classes.