A metallic strip edge flatness monitoring system for a rolling mill comprises one or more thermal imaging devices (105) arranged to monitor temperature or temperature variances across at least one region of interest (108, 115) in the rolling mill. The monitored temperature or temperature variances are input to a flatness control system (107) and a control signal (122) is generated in the flatness control system to modify actuation of actuators (106) in the rolling mill. The region of interest (108, 115) has a width (125) of less than half the width (126) of the metallic strip (101) and comprises a region on each side of the strip. The total width monitored is less than half the total width (126) of the metallic strip.