The severity and nature of potassium deficiency symptoms in Stylosanthes guyanensis (Aubl.) Sw. differed with the varieties involved, the date of harvest and the levels of K at which the plants were grown. Lower levels of K induced severe deficiency symptoms and depressed dry matter production signi-ficantly. Levels of K in plant tissue were greatest in plants receiving K at the highest rate. Plant phosphorus contents were adversely affected, being smallest at high rates of K and greatest at low rates of K.