The Classroom Management Improvement Study (CMIS) was designed to investigate a complex staff development effort in order to provide a clear explication of the treatment in the event that either researchers or practitioners desired to replicate the intervention. The treatment was directed toward introducing effective classroom management procedures to teachers. It consisted of a workshop prior to the beginning of school, a manual of management prescriptions, and a reinforcement workshop 4 weeks after school began. Results show that, prior to the treatment, there was no statistically significant difference between treatment and control teachers' knowledge of classroom management as defined by the CMIS study. Afterwards, treatment teachers exhibited significantly more desired classroom management behaviors than did control teachers. The reinforcement workshop appeared to have little or no effect on treatment teachers' management behaviors other than maintenance. A group of control teachers received a mid-year treatment; results suggested that the mid-year treatment was not as effective as that given prior to the beginning of school. Speculations are made concerning the utility of the CMIS treatment for staff development programs for teachers. (Author/JD)