The elevation of the six subgenera of Penaeus s. lat. to generic level has proven controversial, some accepted the change while others rejected it out of hand. Such a taxonomic reassignment lends itself to testing by the use of molecular techniques. Data are available from studies of cytochrome oxidase subunit I, and 12S and 16S rRNA. However, analyses of these data sets alone, or in combinations, still have not provided a useable taxonomy of Penaeus s. lat. Ideally we should have a taxonomy where both the morphological and molecular data are in agreement. This is especially critical because of the economic importance of penaeid fisheries around the world. Solving many of these taxonomic problems may await the development of new techniques, but in the meantime specific issues using existing data or techniques should be explored. 1) How widely separated molecularly are Farfantepenaeus and Melicertus? since if these two subgenera are indeed close perhaps they should merge into a single genus Melicertus that contains all the grooved shrimp. 2) Penaeus monodon is usually regarded as being closest to the ancestral line; its affinities to other Penaeus s.str. and to Fenneropenaeus, need further research.