In implementing cluster analysis, an analyst has a considerable number of choices of software from which to choose.  This talk will compare four software packages that offer cluster analysis commenting upon the significant features and differences among the four packages.  In the course of presenting the differences between the analysis features in the packages, the statistical theory underlying the particular forms of cluster analysis will be overviewed in order to provide sufficient context to the comparison of features.  The talk will conclude with an assessment of considerations for selection of a package in light of the comparison.