The response of 19 forage grasses to three cutting intervals in the humid mountain region of Puerto Rico was evaluated. Nine Brachiarias, nine Digitarias, and one Cynodon species were evaluated during a 2-year period under cutting management at the Corozal Substation for green forage (GF), dry forage (DF), and crude protein (CP) yields and for dry matter (DM), crude protein (CP), Ca, P, K, and Mg contents. In terms of green forage yield (GFY), the most productive species at the 30-day harvest interval was D. setivalva (PRPI 6402) with 86,794 kg/ ha/year. At the 45- and 60-day harvest intervals, Brachiaria sp. (PRPI 9626) produced 102,116 and 109,213 kg/ha/year, respectively. This species also produced the highest DFY at the 30-day harvest interval with 18,430 kg/ha/year. C. nlemfuensis, var. nlemfuensis (PRPI 2341), stargrass, and B. decumbens (PRPI 5365) produced the highest DFY at the 45- and 60-day intervals with 21,758 and 27,238 kg/ha/year, respectively. The highest CP content at the 30-, 45-, and 60-day intervals was observed on the three Digitaria hybrids, D. pentzii x D. smutzii (PRPI 9621), D. pentzii x D. milanjiana (PRPI 9619), and D. pentzii x D. pentzii (PRPI 9620) with 14.3, 12.0, and 11.1 %, respectively. D. decumbens (PRPI 6439), 'Transvala' Digitgrass, produced the highest CP yield at the 30-day harvest interval with 2, 179 kg/ha/year. Stargrass had the highest CP yield at the 45- and 60-day harvest intervals with 2,141 and 2,030 kg/ha/year, respectively. The P, Ca, Mg, and K contents of the 19 grasses on the average decreased as the harvest interval increased. A sharp decrease (from 1.81 to 1.47 to 1.42%) of the K content of the grasses was observed at the 30-, 45-, and 60-day intervals, respectively. The GFY, DFY, and DM of the 19 grasses increased on the average with the length of the harvest interval. On the other hand, the CP content and yield of the 19 grasses decreased as the harvest interval increased. No significant correlation was obtained between total rainfall, CP, and DFY of the 19 grasses. Significant positive correlations were obtained between DFY of the 19 grasses and average temperature. A significant negative correlation was obtained between average temperature and CP content.