Individual honeybees were trained in two experiments to come for sucrose solution to a target set on a shelf before an open laboratory window. On some visits, the target was presented in the ambient geomagnetic field, and on other visits in a field modified in the vicinity of the target by passing a direct current through a coil under the shelf. The target contained 50% sucrose when it was in one of the two fields and 20% sucrose when it was in the other. Tested subsequently with a pair of targets, one in the ambient field, one in the modified field, and both containing tap water, the animals significantly preferred the target in the field in which they had been given the 50% sucrose during training. Four modified fields, produced with different coils and currents, were discriminated equally well from the ambient field, and performance was as good when the 50% sucrose was given in the ambient field as when it was given in the modified field. Data are provided also to illustrate the excellent discriminative performance attainable when two targets are presented on each training visit — one in a modified field, the other in the ambient field — and choice of one is rewarded with 50% sucrose while choice of the other is punished with mild electric shock. Our results show that foragers attend to magnetic stimuli at the feeding site and that discriminative training techniques are appropriate for the study of magnetoreception and its mechanism in honeybees.