A native Costarican vine, Vitis caribaea, was found growing unaffected by Pierce's disease (PD; Xylella fastidiosa) in the forests surrounding a dying V. vinifera plantation. V. caribaea was tested by inoculation, isolation, ELISA and DNA hybridization and in all cases no bacteria were detected. It was decided that V. caribaea or Agra (its Indian name) is resistant or at least highly tolerant to PD. Crosses of V. vinifera and V. caribaea were made and no compatibility barriers were found, germination of the hybrids seeds was high and a high percentage of fertile plants were produced. Many hybrids were made and planted in the field to test them for resistance to PD. Since some of the F(1) hybrids do transmit resistance when backcrossed to V. vinifera, resistance must be determined by dominant genes. Some F, hybrids, although apparently resistant themselves, are either not transmitting resistance or are doing so in a reduced proportion. Several hybrids developed at the University of Florida were tested, one of these, F 5-8, has led to the establishment of the first successful vineyard in Costa Rica.