1. Cotton plants were grown in water culture in the absence of each of six micronutrients (boron, copper iron, manganese, molybeenum and zinc) in turn. 2. The technique employed is described. 3. The effect of the treatments on growth, yeld and leaf composition is given. 4. The deficiency symptoms are described. 5. The effect of lack of micronutrients on leaf anatomy is also described. 6. The diagnostic volue of the data presented is discussed.