Males of both species defend permanent territories containing enough forage for a herd of females throughout the year. Territories of these two species overlap and bulls, when alone, often remain near each other. On the rare occasions that they interact aggressively, the topi dominates its larger relative. The kongoni is altogether a shyer, less assertive animal. Kongoni breed throughout the year, though with clear peaks in the dry and wet seasons.
Newborn calves spend most of their first month hiding in the grass, like nearly all antelopes.
Topi have a well-defined calving season at the end of the dry season. Topi calves grow very fast. Yearling females can hardly be distinguished from adults by 16 months. At this age most females mate, and then calve at age two. Many males appear full grown by two but few are mature enough to gain territories and breed before three years of age.