The mating patterns of adolescent male chimpanzees (Pan troglodytes) of the Mahale National Park, Tanzania, were studied. Sequential events associated with their copulations were characterized as follows. (1) In encounter, the female tended to approach the male. (2) In precopulation stage, the male often gave courtship displays. (3) In postcopulation stage, the male often groomed the female. (4) In leaving, the female tended to leave first. In every stage, especially during copulation, adolescent males were sensitive to the presence of adult males. The presence of adult males seemed to be enough to prevent adolescent males from copulating with the female. Influences of adult males on copulation of adolescent males are discussed in relation to male-male bonding in chimpanzees.