The right quality control (QC) should ensure the detection of important errors. Statistical QC (SQC) should be included in all QC plans. The Clinical and Laboratory Standards Institute (CLSI) C24A3 provides guidance for the application of SQC in medical laboratories. It describes a QC planning process and provides an SQC selection tool that relates the sigma-metric of a testing process to the medically important systematic error and the rejection characteristics of different SQC procedures. Once the right SQC has been selected, the laboratory must implement SQC right. CLSI C24A3 also provides guidance for establishing run length and control limits.