This article presents a metasynthesis of the literature from 1996 through 2005 on randomized clinical or controlled trials comparing effects of tailored interventions to those of control conditions or other interventions. A search was conducted for publications written in English using the terms "patient-centered interventions," "tailored interventions," and "individualized interventions," using Ovid and Elton B. Stephens Company (EBSCO) Host databases. A total of 245 publications were located after deleting duplicates. An additional six studies were identified from two syntheses of intervention research. A total of 63 studies met the inclusion criteria, and 49 of these reported that tailored interventions were superior to control conditions for one or more of the main outcomes. The evidence strongly supports the efficacy of tailored behavioral interventions and provides beginning support for the efficacy of tailored psychosocial and biological interventions.