This paper reviews the pharmacological properties of Mediterranean-grown citrus species (Citrus L., Rutaceae), including citron (Citrus medica L.), lime (Citrus xauantiifolia [Christm.] Swingle), lemon (Citrus xlimon [L.] Osbeck), bitter orange (Citrus xaurantium L.) and pomelo (Citrus maxima [Burm.] Merr.), as referred to in ancient, medieval and 16th century sources. The virtues of the species reported in these texts were compared to those known to modern science. A much broader spectrum of pharmacological properties was recorded by these early writers than one might expect. The use of the citron and lemon as antidotes for 'poison and venom' is recorded in the very earliest material. According to modern scientific literature the citron and the bitter orange may possess anti-cancer activity, lime may have an immunomodulatory effect in humans, and the pomelo may be useful for treating circulatory problems. Lemons might even ease hangover symptoms. Research is required to confirm these properties.