Stargrass pastures in the humid mountain region of Puerto Rico responded in terms of cattle gain in weight and carrying capacity to fertilization up to 4,480 kg/ha (4,000 lb/acre) yearly of 15-5-10. With 3,136 kg/ha of fertilizer the pastures produced 1,337 kg/ha (1,194 lb/acre) weight gain yearly and had a carrying capacity of 6.8 273-kg steers/ha (2.72 600-lb steers/acre). Average daily gain of .61 kg/bead (1.35 lb/bead) was not affected by variation in rate of fertilization. Neither apparent digestibility of the forage, calculated from total digestible nutrients utilized by the cattle and the dry forage consumed by the grazing cattle, nor in vitro digestibility of the forage samples were affected by changes in fertilization rate. Crude protein content of the forage consumed by the grazing cattle was very high at all fertilizer rates, ranging from 17.4 to 29.1% throughout the year. Forage content of Ca, P and lignin was not affected by fertilizer rate or season of the year.