APC system health should be monitored to ensure continuing effectiveness. The monitoring must include both input and output monitors. The proposed indicators of the overall health of the system include metrics to monitor the systematic variation of the output and the relationships of the input adjustments to the output as well as the acceptability of the output. Additional indicators are proposed to track the adjustments made by the APC system. Some indicators should be included to monitor the quality of the data, which is critical to the successful implementation of APC.