A preliminary control chart based on individual observations for detecting a shift in either the mean or variance or both is developed from a likelihood ratio test. The advantages over use of theXcontrol chart and moving range control chart are improved detection of sustained shifts, in addition to improved diagnostic information indicating multiple shifts and whether an out-of-control signal is primarily due to a shift in the mean or variance or a combination. Approximate control limits, determined from simulation, are given for the proposed control chart.