Since the 1960s, in many parts of the world, large psychiatric were closed down and people were treated in outpatient clinics, day centres or community mental health centres. Rising readmission rates suggested that this type of community care may be less effective than anticipated. In the 1970s case management arose as a means of co-ordinating the care of severely mentally ill people in the community. To determine the effects of case management as an approach to caring for severely mentally ill people in the community. Case management was compared against standard care on four main indices: (i) numbers remaining in contact with the psychiatric services; (ii) extent of psychiatric hospital admissions; (iii) clinical and social outcome; and (iv) costs. Electronic searches of CINAHL (1997), the Cochrane Schizophrenia Group's Register of trials (1997), EMBASE (1980-1995), MEDLINE (1966-1995), PsycLIT (1974-1995) and SCISEARCH (1997) were undertaken. References of all identified studies were searched for further trial citations. The inclusion criteria were that studies should be randomised controlled trials that (i) had compared case management to standard community care; and (ii) had involved people with severe mental disorder mainly between the ages of 18-65. Studies of case management were defined as those in which the investigators described the intervention as 'case' or 'care' management rather than 'Assertive Community Treatment' or 'ACT'. A study was carried out to test the reliability of the inclusion criteria. Categorical data were extracted twice and then cross-checked, any disagreements being resolved by discussion. Odds ratios and the number needed to treat were estimated. Continuous data collected by a measuring instrument was only included if the instrument (i) had been described in a peer-reviewed journal; (ii) was a self-report or had been completed by an independent rater; and (iii) provided a summary score for a broad area of functioning. Normally distributed continuous data were included if means and standard deviations were available. Non-normal data were included if analysed either after transformation or using non-parametric methods. Tests for heterogeneity were conducted. Case management increased the numbers remaining in contact with services (for case management odds ratio = 0.70; 99%CI 0.50-0.98; n=1210). Case management approximately doubled the numbers admitted to psychiatric hospital (OR 1.84; 99% CI 1.33-2.57; n=1300). Except for a positive finding on compliance, from one study, case management showed no significant advantages over standard care on any psychiatric or social variable. Cost data did not favour case management but insufficient information was available to permit definitive conclusions. Case management ensures that more people remain in contact with psychiatric services (one extra person remains in contact for every 15 people who receive case management), but it also increases hospital admission rates. Present evidence suggests that case management also increases duration of hospital admissions, but this is not certain. Whilst there is some evidence that case management improves compliance, it does not produce clinically significant improvement in mental state, social functioning, or quality of life. There is no evidence that case management improves outcome on any other clinical or social variables. Present evidence suggests that case management increases health care costs, perhaps substantially, although this is not certain. In summary, therefore, case management is an intervention of questionable value, to the extent that it is doubtful whether it should be offered by community psychiatric services. It is hard to see how policy makers who subscribe to an evidence-based approach can justify retaining case management as 'the cornerstone' of community mental health care. Case management is compared to the main alternative approach (ACT) in a forthcoming Cochrane review.