Cottonseed meal, which had been mechanically extracted, was treated with varying quantities of formaldehyde (HCHO) ranging from 0.125 to 1.500 per cent (w/w). Solubility of the nitrogen molar saline in untreated meal was 17.3 per cent, and in HCHO-treated meals ranged from 10.2 to 3.2 per cent. Solubility was related by a quartic relationship to the quantity of HCHO added. when incubated for 24 hours with rumen liquor at 39¦C, 36.5 per cent of the nitrogen in the untreated meal was liberated as ammonia and between 30.6 and - 0.5 per cent for the HCHO-meals. Organic matter and apparent nitrogen digestibilities of the meals were depressed by approximately 1 and 0.8 units respectively for each 0.1 per cent HCHO added. Utilization of digested nitrogen was not significantly increased as a result of HCHO treatment. Sheep were held in yards and received either 400 g wheat or 300 g wheat and 100 g of a number of cottonseed meals. Although three of the meals had been treated with HCHO, there were no significant differences between diets in either wool production or liveweight change. Sheep grazed at 25 sheep per acre received as a supplement 150 g wheat and 50 g of cottonseed meal or HCHO-meal per day given twice weekly. Again there were no significant differences in productivity of the sheep attributable to the diet.