It has long been observed that independent laboratories differ in reporting the results of repeated experiments. The problem is to detect those laboratories that might be considered aberrant. Previous analyses have been based on an analysis of variance framework or on subset selection for the detection of aberrant laboratories. The present procedure is also based on an ANOVA model but uses a Bayesian estimate of the number of aberrant laboratories. Subsequent to the determination of the aberrant laboratories, a linear model is used to separate sampling and laboratory effects.