The larvae of Perileucoptera coffeella, a leaf miner, is one of the main pests attacking coffee plantations. Caffeine is the major alkaloid in this crop and may have a role in insect resistance. Since there is genetic variability in both resistance to the coffee leaf miner and in caffeine content among different coffee species, we investigated the role of this alkaloid as an antiherbivory compound. Coffee plants containing different levels of caffeine were exposed to oviposition of the insect, and the caffeine content and damaged leaf area were evaluated. The same procedure was carried out with interspecific hybrids between C. arabica and C. racemosa, varying in resistance against the leaf miner. In addition, plants were exposed to the insect, but one leaf of each pair was protected from oviposition with paper bags. In another experiment, leaf disks from plants with known susceptibility to attack by the leaf miner were infiltrated with 0-2% aqueous caffeine solutions and exposed to oviposition. When one leaf of a pair was protected from the insect, there was an increase in caffeine in the infested leaves, particularly in younger leaves. None of the experiments established a significant correlation between reduction of leaf damage and caffeine content of the tissue. The results indicate that P. coffeella is well adapted to coffee, and it has evolved a mechanism to tolerate the potentially toxic effects of caffeine.26614471464