Leaf proteins from 21 sour orange (Citrus aurantium L.) cultivars and relatives were studied for chemotaxonomical purposes. Soluble proteins were separated by polyacrylamide gel electrophoresis. Using the patterns obtained it was possible to distinguish the different species and cultivars. Multivariate analysis was carried out, based on the densitometric readings of the proteinograms. The results of the principal components analysis showed five cultivars ‘Bergamot’ from Alcanar, ‘Bergamot Melarosa’, ‘Bouquet de Fleurs’, ‘Amargo Clementino’ and ‘Nansho daidai’ that segregated from the main cluster in the three dimensional plot. In the dendrogram obtained, these five cultivars branched at dissimilarity levels over 2.0. The possible origin of the cultivars is discussed.