The view that the mandrill (Mandrillus sphinx ) and the drill (M. leucophaeus) are sympatric is examined. Museum records are collated and mapped and evidence that the former species occurs north of the Sanaga river, and the latter exists to the south, are critically evaluated. The distribution and possible speciation patterns of the genus are summarised. Explanations for differences between drill and mandrill are suggested, and the advisability of employing a superspecies classification is considered.