Fortuna Agricultural experiment substation, Juana Díaz, in the semiarid south coast and Isabela agricultural experiment substation in the humid north coast of Puerto Rico were selected as representative locations in each region. Field work was conducted during the winter at Fortuna: drip, microsprinkler and furrow irrigation increased commercial yield of (mature green + red) staked tomatoes by 112%, 82%, 37% compared with control plots during the winter of 1987. Values of growth parameters were lowest in the nonirrigated plots at P = 0.05. Based upon tensiometer readings, total water application (mm per season for 120 days) was 1050 in furrow, 611 in microsprinkler and 386 in drip irrigation, respectively during the winter at Fortuna. Seasonal net irrigation requirement (NIR, mm) was estimated with the modified Blaney-Criddle USDA-SCS method and was 336 in normal years and 409 in dry years at Fortuna; 253 in nomiai years and 311 in dry years at Isabela in the winter. Total NIR was 399 in normal years and 492 in dry years at Fortuna; 262 in normal years and 357 in dry years at Isabela in summer, respectively. CU at Fortuna was 7 to 7.6% higher than CU at Isabela. NIR at Fortuna was 25 to 35% higher than at Isabela. At Fortuna sweet pepper yield and values of growth parameters were lowest in the nonirrigated plots at P = 0.05 during the winter and summer. Drip, micropsprinkler and furrow irrigation increased commercial yield of sweet pepper by 168%, 115.5%, 52% compared to that of control plots during the winter; and 186%, 119.6%, 85% compared to control plots during the summer, respectively. Silver coated plastic mulch increased the yield during winter and summer. Growth parameters versus days after transplanting relationships were of sigmoidal type. Based upon tensiomenters at 30 cm depth and a tension reading of 15—45 cbar, total water application (mm per season for 120 days) was 1260 in furrow, 524 in microsprinkler and 406 in drip irrigation during the winter; and 951 in furrow, 542 in microsprinkler and 419 in drip irrigation during the summer, respectively. No field work was conducted at Isabela. Seasonal net irrigation requirement (NIR, mm) of sweet peppers was 341 for winter and 352 for summer in normal years.