Transposon tagging can work. Even though most of our understand- ing about the factors that contribute to a successful tagging experiment has been accumulated from a limited number of experiments using different transposable elements in different genetic backgrounds, it is still possible to draw some conclusions regarding the best experimental strategies for gene tagging. In our experience, Spm has proved to be a good element for transposon tagging. The frequency of recovering mutable alleles in- duced by Spm is not significantly different from that for Ac-Ds or for Mu 6 (summarized in Ref....