1-Oxo- and 1,3-dioxo-2-(2,6-dioxopiperidin-3-yl)isoindolines substituted in the 4- and/or 7-position of the isoindoline ring and optionally further substituted in the 3-position of the 2,6-dioxopiperidine ring reduce the levels of inflammatory cytokines such as TNF.alpha. in a mammal. A typical embodiment is 1,3-dioxo-2-(2,6-dioxopiperidin-3-yl)-4-m- ethylisoindoline