outlier detection using cluster analysis

In SAS, a quick-and-dirty approach to outliers using cluster analysis is PROC FASTCLUS. The documentation for this procedure includes an example to detect outliers. Try several different options (especially the LEAST option of the PROC FASTCLUS statement) to determine whether this procedure works for your data. Note that PROC FASTCLUS works only with interval/ratio/continuous valued variables, unless you stratify your data using separate analyses for nominal variables using the SAS BY statement.