An inventory was completed of the woody vegetation of a post oak flatwoods near Lake Sara, Effingham County, Illinois. This 3 ha forest, located in the Southern Till Plain Natural Division of Illinois, has a stand composition of 280.3 stems/ha (above 10 cm dbh) and a basal area of 19.5 sq m/ha. Of 12 woody species present, post oak is the leading dominant accounting for more than 50% of the importance value (IV of 104.8). Black oak ranks second in IV, followed by blackjack oak, white oak, shingle oak, and three hickory species. Tree seedlings average 25,209 stems/ha, but few saplings are present (41 stems/ ha), probably the result of yearly fires.