BACKGROUND Tardive dyskinesia (TD) is a potentially disfiguring movement disorder of the orofacial region often caused by use of neuroleptic drugs. A wide range of strategies has been used to help manage TD and, for those who are unable to have their antipsychotic medication stopped or substantially changed, the calcium-channel blocking group of drugs (diltiazem, nifedipine, nimodipine, verapamil) has been suggested as a useful adjunctive treatment. OBJECTIVE To determine the effects of calcium-channel blocker drugs (diltiazem, nifedipine, nimodipine, verapamil) for treatment of neuroleptic-induced TD in people with schizophrenia, schizoaffective disorder or other chronic mental illnesses. METHODS Electronic searches of Biological Abstracts (1982-2000), Cochrane Library (Issue 4, 2000), Cochrane Schizophrenia Group's Register of trials (November 2000), EMBASE (1980-2000), LILACS (1982-2000), MEDLINE (1966-2000), PsycLIT (1974-2000), and SCISEARCH were undertaken. References of all identified studies were searched for relevant citations. Principal authors of trials were contacted. METHODS Randomised clinical trials comparing calcium-channel blockers to placebo or no intervention for people with both TD and schizophrenia or serious mental illness were reliably selected. METHODS Data were to have been independently extracted and analysed on an intention-to-treat basis. The relative risk (RR) and 95% confidence intervals (CI) of homogeneous dichotomous data were to have been calculated using a random effects model, and, where possible, the number needed to treat calculated. Weighted mean differences (WMD) were to have been calculated for continuous data. RESULTS No trials were included. Seven studies were excluded; five were not randomised and two small randomised crossover studies provided no usable data. Two more small randomised controlled trials await assessment. The authors have been contacted for relevant information. CONCLUSIONS Based on currently available information, no confident statement can be made about the effectiveness of calcium-channel blockers for treating people with neuroleptic-induced tardive dyskinesia. Before evaluation of these drugs in larger randomised controlled trials, clinicians should carefully weigh up the possible benefits against their potential adverse effects.