The drill is a short-tailed monkey up to 70 cm (28 in) long, similar in appearance to the mandrill, but lacks the bright blue and red on the face of that species.

Mature males have a pink lower lip and white chin on a dark grey to black face with raised grooves on the nose.

Two subspecies of drill are accepted by some authorities,[4] but are not considered distinct by others:[5] Their closest relative is the mandrill (Mandrillus sphinx), found from southern Cameroon through mainland Equatorial Guinea (Rio Muni), Gabon and into the Congo.

The females give birth to a single baby; twins have been recorded once at the Drill Rehab & Breeding Center in Nigeria.

The diet is primarily frugivorous, taking a wide range of fruit, but they also eat herbs, roots, eggs, insects, and small mammals on occasion.