The performances of three procedures for treatment of outliers in normal samples are evaluated. The first procedure is the sequential application of the usual maximum residual test. The largest observation is declared an outlier if the largest studentized residual exceeds a predetermined value. If one outlier is detected, the test is repeated on t.he remaining observations, the process continuing until no further outliers are detected. In the second procedure the two largest observations are declared outliers if the sum of the two largest studentized residuals exceeds a predetermined value. In the third procedure the two largest observations are considered outliers if the ratio of the corrected sum of squares omitting these values to the total corrected sum of squaresis less than a critical ratio. The performances of these procedures are evaluated for samples in which two of the observations have means different from the common mean of the remainder of the sample.