OBJECTIVE: /st> Many patients with schizophrenia are not treated in line with evidence-based guidelines. This study examines the large-scale implementation of the National Multidisciplinary Guideline for schizophrenia in the Netherlands. DESIGN: /st> Observational, prospective study, with repeated measurement. SETTING: /st> Thirty mental healthcare teams in different regions of the Netherlands. PARTICIPANTS: /st> Three hundred and fifty-nine clinicians with different professional backgrounds and 1489 patients suffering from schizophrenia. INTERVENTION: s) Six evidence-based interventions for schizophrenia were implemented, in the context of a quality improvement collaborative: assertive community treatment (ACT) or its adapted version functional assertive community treatment (FACT), cognitive behavioural therapy, psycho-education, family interventions, individual placement support and pharmacotherapy. MAIN OUTCOME MEASURE: s) Professional performance, social functioning and relapse rates. RESULTS: /st> Improved professional performance, in line with guidelines. Availability of (F)ACT improved from 23 to 60%. Individual Placement Support improved from 20 to 53%. Complete care plans were composed for 38% of the patients and routine outcome monitoring was introduced in most teams. Social functioning improved slightly (HoNOS mean: from 6.2 to 5.6). Relapse rates did not improve during the course of the study. CONCLUSIONS: /st> An intensive implementation programme can result in an improved delivery of evidence-based care, increased continuity of care and slightly improved outcomes for individuals with schizophrenia. More rigorous research designs have to confirm these findings.