Bilberry leaves (Vaccinium myrtillus L.) were one of the most frequently used antidiabetic remedies of plant origin before the discovery of insulin. During the last century, many animal, clinical and phytochemical studies have been undertaken with this plant and its extracts and are summarized here. Overall, it must be concluded that the results were more or less disappointing and could not support the traditional use of bilberry leaves against diabetes mellitus which is sometimes recommended even up to the present day.