We investigated two Black Prairie relict sites at Sixteen Section Prairie, Oktibbeha County, Mississippi, in 1994-95. We documented 152 species of vascular plants, including 7 considered imperiled or critically imperiled in the state and 4 proposed for listing as possibly imperiled, imperiled, or critically imperiled. We delineated three different plant communities: the open prairie community, the prairie cedar woodland community, and the chalk outcrop community. A comparison of our findings with historical accounts of Black Prairie plant communities suggests recent (<150 years) changes in Black Prairie plant community structure. Using floristic data generated in this study, we also found evidence to further support the hypothesis that there are substantial similarities between Mississippi and Arkansas blackland prairies. At the same time, our data suggest that Mississippi and Texas blackland prairies differ in overall character.