Higher level of KCI application stimulated both leaf area index and leaf area duration in all cassava varieties, while the leaf and tuber number of the bitter varieties (high cyanide-level varieties) decreased in proportion to the level of KCI application. The root/shoot (R/S) ratio and harvest index (HI) were negatively related with the level of KCI application in all cassava varieties. The bitter varieties obtained the lowest R/S ratio at the level of 100 - 150 kg KCI ha^-1, while the sweet varieties (low cyanide-level varieties) acquired the highest values at the level of 50 - 150 kg KCI ha^-1. Also, the sweet varieties showed the lowest HI at the level of 250 kg KCI ha^-1, but the bitter varieties at the level of 150 kg KCI ha^-1. At 6 - 8 months after planting, the sweet varieties tended to obtain higher starch content of roots (tubers) at the level of 50 - 150 kg KCI ha^-1, while the bitter varieties at the level of 150 - 250 kg KCI ha^-1. Relatively lower level of 50 - 150 kg KCI ha^-1 was more appropriate for decreasing hydrocyanic acid (HCN) content of roots (tubers) in the sweet varieties at the harvest time, and the level of 250 kg KCI ha^-1 was adequate to decrease not only HCN content of leaves but also that of roots (tubers) in the bitter varieties during the growing period. To obtain higher yield and starch content of tubers, and lower HCN content of roots (tubers), it was recommended that the sweet varieties are applied with the level of 50 - 100 kg KCI ha^-1 and the bitter varieties with the level of 150 - 200 kg KCI ha^-1, respectively, in Latosol soils of Bogor areas, West Java.