Born in Kampala, he began his professional boxing career in 1976 when he won a four-round decision over Kurt Hombach in Copenhagen, Denmark.

Included in those victories were defeats of Alipata Korovou for the Commonwealth Middleweight Title and a 10-round decision of former U.S. olympic gold medalist Sugar Ray Seales.

The fight proved much more difficult for Leonard as Kalule repeatedly landed straight lefts and fought on an almost even ground for the first five or six rounds.

Slowly Leonard started to take control and in the 9th round ended the fight and Kalule's reign as WBA Champion.

[2] Kalule fought on until the beginning of 1986 and managed to win the European Middleweight Title and defend it successfully against future world champion Sumbu Kalambay.