Elevated rumen ammonia levels in sheep on high nitrogen kikuyu (Pennisetum clandestinum Hochst) grass were indicative of a protein/energy imbalance in the grass. To correct the imbalance, grass containing 22% crude protein required maize meal supplementation of at least 20% on a dry basis. Unsupplemented high nitrogen kikuyu grass had a low dry-matter intake and digestibility. The efficiency of conversion of plant nitrogen into microbial protein in the rumen was probably poor and resulted in a large proportion of the ingested nitrogen being excreted in the urine. Maize meal supplementation improved the dry-matter intake and significantly increased the apparent retention of nitrogen and gross energy of the kikuyu grass.