Dapsone (4,4'-diaminodiphenylsulfone, DDS) was synthesized a century ago and continues to be a powerful therapeutic tool in many skin diseases. We have tried to retrieve and present the available knowledge and relevant information on this old but still very useful drug with the hope of encouraging and guiding practicing dermatologists to adapt it for various indications. Our objective is to familiarize the clinician with how this agent works, in what disease states it is effective, how to administer it, what adverse effects may occur, and how to monitor the patient receiving this drug.