A report is given of the development and implementation of a training manual for eighth-grade mathematics teachers in the Netherlands. The manual is research-based on process-product correlations of effective classroom practices. To test the effectiveness of a 6-hour training period using the manual, nine experienced mathematics teachers were observed with the same class for six lessons before the training. Following their participation in training with the manual over an 8-week period, the teachers were observed again. The focus of the obsrevations was on classroom management and instruction. It was concluded that the training and the training manual can change teacher behavior. Tables present comparisons in behaviors before and after using the training manual. (JD)