Studies were conducted in the central mountainous region of Puerto Rico to determine the adaptability of 18 pummelo clones. Data on fruit number, weight and yield efficiency were collected during three consecutive crop years beginning the fourth year after planting. Clones Dry Pink, Thong Dee White and African Seedling were the best in terms of total number of fruits produced per tree, Production increased with age from over forty fruits for four-year-old trees to over sixty fruits per tree for six-year-old trees. Fruit weight per tree also increased with age, reaching a maximum of 87 kg of fruit for six-year-old trees. Clones Dry Pink and Thong Dee White were the best in terms of total fruit weight. Yield efficiency measured in terms of number of fruits per cm of stem diameter also increased with age from an average of 5.50 for four-year-old trees to 7.55 for six-year-old trees. Best yield efficiency was obtained with clones Dry Pink, Reinking, Thong Dee White and Green Favorite. These results indicate an excellent adaptability of the pummelo to the soil and climate conditions prevailing in the central mountainous region of Puerto Rico.