The lesser spot-nosed guenon (Cercopithecus petaurista Schreber 1774) was known to range, historically, in the southwestern or Casamance region of Senegal (Dupuy 1971); its status in that country has been questionable in more recent times1 (Figure 1). The recent sightings of a lesser spot-nosed guenon in southeastern Senegal (12º39’N, 12º13’W) to be reported here appear to be the first record for this species in the Kedougou (formerly, Tambacounda) region. The guenon was seen by researchers at the Fongoli study site where chimpanzees (Pan troglodytes verus) have been observed continuously since April 2001. Although Guinea baboons (Papio hamadryas papio), patas monkeys (Erythrocebus patas), vervet monkeys (Chlorocebus aethiops sabeus), and Senegal bushbabies (Galago senegalensis) are commonly seen, the lesser spot-nosed guenon had never been seen at Fongoli in the four years of continuous study by researchers before this sighting, and it was never seen again in the following four years after the series of observations described here.