OBJECTIVE: We sought to systematically review the literature related to oral lichenoid lesions (OLLs) and amalgam restorations. STUDY DESIGN: Cohort and case-controlled studies (no randomized controlled trials or controlled clinical trials available) were reviewed with respect to inclusion criteria and data on patients with OLLs, treatment interventions, and the measurement of outcomes. RESULTS: Fourteen cohort and 5 case-controlled trials met the criteria. The study population consisted of 1158 patients (27% male and 73% female; age range, 23-79 years). From 16% to 91% of patients had positive patch test results for at least 1 mercury compound. Of 1158 patients, 636 had to have their restorations replaced. The follow-up period ranged from 2 months to 9 1/2 years. Complete healing ranged from 37.5% to 100%. The greatest improvements were seen in lesions in close contact with amalgam. CONCLUSIONS: Protocols must be standardized to obtain valid results. The replacement of amalgam restorations can result in the resolution or improvement of OLLs. Patch testing seems to be of limited value. The topographic relationship between an OLL and an amalgam restoration is a useful--but not conclusive--marker.