In this article, variations in particle sizes (F50 and P 50) obtained from feeding and ground coals in a vertical roller mill of AS Cement Factory (Turkey) were investigated using control charts and process capability analysis. From results of calculations, the control charts mostly indicated that the variations in particle sizes of the feeding and ground coals are outside the control and specification limit and are not statistically stable. Additionally, a viewpoint was that the process capabilities were inadequate. The reason for this might be the different feeder and bin discharge problems of coal and the careless behaviors of laborers. © 2013 Taylor and Francis Group, LLC.