A sodium hydroxide spray treatment of wheat straw was evaluated in experiments on twenty male calves. Sodium hydroxide solutions of 0, 3·3, 6·7 and 10% concentration were sprayed on ground wheat straw (Exp. 1) and chaffed wheat straw (Exp. 2) at the rate of 1000 litres per tonne. The straws were not washed. The treated straw was then fortified with groundnut cake, molasses and a mineral supplement. In Exp. 1 rations were prepared in bulk and dried and in Exp. 2 the rations were prepared daily and fed wet. A 1 kg green forage supplement was fed daily to all animals. The dry-matter intake (g/kg body weight0·75), and organic matter digestibility coefficients (%) for the four levels of alkali treatment were 86, 95, 78, 66 and 53, 63, 63 and 62 respectively in Exp. 1 and for Exp. 2 they were 95, 121, 105, 89 and 55, 70, 71 and 71. The intake of digestible organic matter thus increased by 25 and 63% in Exp. 1 and Exp. 2, respectively. Nitrogen, calcium and phosphorus retentions were not adversely affected up to 3·3% alkali treatment in Exp. 2. The effectiveness of this spray treatment in terms of increased nutritive value is compared with that of the older Beckmann method of alkali treatment. Treatment costs are also compared.