The Inter-Regional Research Project, No.4 (IR-4) is a USDA-CSRS and ARS sponsored program to develop data required by the EPA for pesticide, biorational and drug labels for minor or speciality uses. In Puerto Rico, IR-4 pesticide research efforts have been directed towards determining efficacy, effect on yield, residues and phytotoxicity data to obtain tolerances for the pesticide/crop combinations: ametryn/yam, tanier and cassava; prometryn and metribuzin/pigeon pea; paraquat and glyphosate/acerola; chloramben and paraquat/pigeon pea. Most of the data has resulted in Federal or Special Local Need registrations. Field and residue work has also been completed for fluvalinate and captafol/coffee; methomyl/sugar cane; acephate and esfenvalerate/ pineapple; paraquat/cassava. tanier and yam and; fluazifop-p-butyl, fenallliphos and oxamYl/cooking peppers. With IR-4 collaboration, tolerances and exemptions established for pesticide residues on bananas have been extended to plantains, from sweet potatoes to yam and from peas to pigeon pea. The inclusion of specific crops grown in Puerto Rico and the Caribbean Basin into EPA's crop groupings has also been achieved. Problems affecting tolerance approvals and label development by EPA are discussed.