It was developed an application using Excel(MR), called CEPLAB, aiming at controlling statistical laboratory analyses quality carried out in treatment of liquid effluents. The CEPLAB allows determining the special occurring causes, acting in the process variation, which turns the process unstable. Once detected, the responsible members for the processing control may work in order to eliminate such special causes, producing in this away a stable base for the quality analysis to preserve and give continuous improvement. After the process reaches its own stability, the frequency of analysis can be minimized, and therefore, this procedure will reduce costs. In order to carry out the Statistical Control, the software has its own tools for calculating the Capability Potential index (Cp) and of the Process Performance (Cpk), Control Charts and Graphics of measurements and amplitude, process stability analyses, also a Histogram to verify the Process Normality. The software may be utilized for all types process (Physical, Chemical and Biological), over which measurements are realized.