A method for trend detection, Trigg's technique [Oper. Res. Q. 15, 271 (1964)], has been investigated for use in monitoring trends in control data produced by multitest continuous-flow analyzers. Simulated trend data were used to optimize the method. Actual control data were analyzed retrospectively to determine the frequency of trends and the accuracy of several parameters obtained from Trigg's method. The prospective use of the technique has successfully uncovered important trends. Criteria for the interpretation of the Trigg's trend data are suggested and an algorithm for the computer implementation of Trigg's calculations is included.