Recently, many new formulations of older drugs have been marketed as sustained-release preparations. Only some of these compounds have scientific rationale supporting their development. At least two inherent properties of a drug are desirable in considering its reformulation into a sustained-release entity. On of these properties is the demonstration of a concentration/response relationship together with a short plasma elimination half-life and inactive or uncharacterized activity of any generated metabolites. The second property is the production of transient side effects associated with dissolution and/or peak concentrations. When neither of these conditions is satisfied, then a sustained-release preparation may offer no advantages over the conventional formulation. The literature on indomethacin was examined with respect to the above conditions and it was concluded that its marketing as a sustained-release preparation is not justified and that investigations have failed to demonstrate clinical advantages of this new formulation.