Six sound patterns are important in social communication of the black and white colobus, Colobus guereza, in the Budongo forest, Uganda. The loud roaring of adult males seems to function in intergroup spacing. The snort of adult males may be a threat or an alarm. A soft purring, rarely heard, accompanies a group movement. A cawing sound is used by adult females, juveniles, and infants in situations of mild distress or threat. Squeaks and screams are used by adult females, infants, and juveniles in acute distress. A non-vocal sound, the tongue click, is employed in territorial defense. The characteristics of these sounds are interpreted in light of the social organization of this species which is territorial, with an average group of eight animals, typically with only one adult male. Signals used primarily in intertroop communication are discrete, while those used for signalling within the troop are graded.