Higher level of KCl 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 KCl application. The root/shoot (R/S) ratio and harvest index (HI) were negatively related with the level of KCl application in all cassava varieties. The bitter varieties obtained the lowest R/S ratio at the level of 100 - 150 kg KCl ha-1 , while the sweet varieties (low cyanide-level varieties) acquired the highest values at the level of 50 - 150 kg KCl ha-1 . Also, the sweet varieties showed the lowest HI at the level of 250 kg KCl ha-1 , but the bitter varieties at the level of 150 kg KCl 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 KCl ha-1 , while the bitter varieties at the level of 150 - 250 kg KCl ha-1 . Relatively lower level of 50 - 150 kg KCl 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 KCl 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 KCl ha-1 and the bitter varieties with the level of 150 - 200 kg KCl ha-1 , respectively, in Latosol soils of Bogor areas, West Java.