Substituted 2-(2,6-dioxopiperidin-3-yl)phtalimides and l-oxo-2-(2,6-dioxopiperidin-3-yl)isoindolines reduce the levels of TNF alpha in a mammal. Typical embodiments are 1-oxo-2(2,6-dioxo-3-methylpiperidin-3-yl)-4,5,6,7-tetrafluoroisoindoline and 1,3-dioxo-2-(2,6-dioxo-3-methylpiperidin-3-yl)-4-aminoisoindoline.