Objective: To provide a description of the service delivery model of an assertive community treatment (ACT) team in the management of a group of severely mentally ill patients and examine the effectiveness of this team in reducing readmissions to a psychiatric inpatient service. Method: A clinical case audit was performed on a single day in September 2001. Admission episodes and duration were collected for patients registered with the team in the 12 month period prior to ACT and for a period of 12 months ending on the day of the audit. Forty-three patients were registered with the team at the time of data collection. The majority (79%) were diagnosed with schizophrenia and there were high rates of comorbidity (76%) and disability (mean Global Assessment of Functioning score 45.9). The main outcome measures were the number of readmissions and readmission days before and after the institution of ACT. Results: The mean number of readmission days reduced from 70.9 to 10.2 (p < 0.05) following the institution of ACT. Conclusion: Assertive community treatment conducted in a naturalistic clinical environment is effective in signi?cantly reducing the number of readmission days in a group of patients suffering from long-term and persistent severe mental illness.