Methanex is the largest methanol producer in the world, the Cape Horn Plant accounts for 2800.000.000 MTon of its total production. Three production lines (a fourth under construction) are controlled by a combination of DCS and equipment monitoring systems. A 20,000 Tag PI System is installed, collecting data from the process control, equipment monitoring systems, lab data, and equipment surveys (using hand held devices). The large production volume per unit implies that quality control and early alert on product specification deviations are critical. The same applies to the overall process monitoring to prevent sub-standard conditions, large deviations, reduced throughput and failures. By the online collection and the analysis of lots of variables, the PI System provides an important support to the process supervision. In the presentation two applications will be shown (a) Use of PI SQC to monitor the "TaxonomyItemHtml cause variables" that determines the product quality, and then an early information as referred to the Lab Data (b) Use of the PI System and advanced statistical techniques for overall process monitoring for the early detection of "out of pattern" operating conditions.