A field experiment was conducted at the Lajas Experiment Substation in the semiarid region of Puerto Rico to evaluate the production and persistence of 8 tropical grasses, Cynodon nlemfuensis Star, C. dactylon Coastcross-1, C. plectostachyus Star, Panicum maximum USDA Pl291047, Makueni, Guinea and P. maximum USDA PI 259553, and the naturalized pasture Dichanthium annulatus pajon. Small plots were grazed at 3- to 5-week intervals for 2 years. P. maximum USDA PI 259553 and Makueni were highly productive in the semiarid,.region, as well as in previous experiments in humid regions in Puerto Rico. They are highly recommended for grazing trials. P. maximum Makueni and USDA PI 291047 were the most productive during the first year, although they were not significantly different (P=0.05) from P. maximum USDA PI 259553 and Common Guinea, and Cynodon plectyostachyus Star. The production of C. nlemluensis Star was similar to that of Dichanthium annulatus but higher than that of C. dactylon Coastcross-1 (P=0.05). The average production for all grasses declined at the beginning of the year, during the cool short days in February and March, 1983, without any significant difference (P=0.05) among species and cultivars. Production increased at the beginning of the rainy season, but it was low at the peak of the rainy season because of trampling in poorly aerated and compact soils. C. plectostachyus Star was the most productive grass during the second year of experiment, although it was not significantly different (P=0.05) from P. maximum USDA PI 291017 and 259553 and cultivar Makueni. The production of Common Guinea and that of D. annulatus were. similar and higher than that of C. nlemfuensis Star and C. dactylon Coastcross-1 (P=0.05), which did not persist at the end of the experiment. Forage production during the second year was lower than in the first year because of less rainfall in 1983. The mean CP content of all grasses varied from 11.29 to 14.05, except that of D. annulatus, which was only 9.73%. CP content was lower during the periods of maximum forage production.