A field trial of transformed Coffea canephora for the synthesis of the Bt protein cry1Ac against coffee South-American leaf miner was performed in French Guiana. Almost all the transformed clones were highly resistant against Leucoptera coffeella. The strategy of plant selection requires the creation of lines synthesizing large amounts of insecticidal protein. The transgenic protein in the leaves of 15 independent transformed clones was quantified once. A significant variability in the transgenic protein concentration was seen among the clones. The potential of the used genetic construct seems interesting.