This study shows that the biochemical inertness of the genus Micrococcus makes the API microtitre strip an unsuitable technique by which to identify species within the genus and that colony pigmentation is an invalid character with which to speciate the genus Micrococcus. The genus Micrococcus forms a heterogeneous group of organisms when ribotype group and pulsed-field gel electrophoresis (PFGE) is considered. The use of two restriction enzymes forms different ribotype groupings within the genus. In this study M. kristinae, M. varians and the majority of M. sedentarius formed homogeneous core ribotype profiles. M. luteus and M. lylae formed heterogeneous ribotype and PFGE groups. The ability of M. lylae and M. sedentarius to belong to M. luteus ribotype groups demonstrates a genetic relationship between these species and M. luteus. Restriction enzyme analysis (REA) and PFGE were the most useful techniques for typing the micrococci. By PFGE M. roseus has a genome size of 3,387 kilobases (kb) which is approximately 30% larger than other members of the genus, which have genomes of between 1,823 and 2,598 kb, and may warrant generic status. By REA and ribotyping it was shown that people carry a clonal population of M. luteus over a period of time.