To assess the effectiveness of consultation-liaison services, involving mental health professionals working to advise and support primary care professionals in the management of depression. Studies of consultation-liaison for depression in primary care were identified from a systematic search of electronic databases, augmented by identification of papers from reference lists, published reviews and from hand searching. Data on study quality, intervention characteristics and outcomes were extracted by two reviewers, and outcome data were meta-analyzed. Five studies met the criteria. There was no significant effect of consultation-liaison on antidepressant use (risk ratio 1.23, 95% CI 0.91 to 1.66) or depression outcomes in the short- (standardized mean difference -0.04, 95% CI -0.21 to 0.14) or long-term (standardized mean difference 0.06, 95% CI -0.13 to 0.26). Evidence concerning consultation-liaison for depression in primary care remains limited, but the existing studies do not suggest it is more effective than usual care. Further research is required to explore the mechanisms by which consultation-liaison might be made more effective, including the potential role of consultation-liaison in combination with other models of care, and in other patient populations. Copyright 2010 Elsevier Inc. All rights reserved.