Determination of anthocyanins in fresh and concentrated juices can be a parameter for the assessment of authenticity and quality of blood orange juices. This work reports an HPLC/UV-Vis method developed for quantitative determination of anthocyanins in blood orange juices, by using a calibration curve obtained for standard cyanidin-3-glucoside. Samples analysed have been obtained from fruits of different trees (one for each of the varieties: 'Moro', 'Tarocco', 'Sanguinello' and 'Sanguinello nocellare') harvested about every 15 days during the 1998 productive season. Seasonal variation has been also evaluated. HPLC results were compared with spectrophotometric measurements, using a calibration curve obtained for cyanidin-3-glucoside solutions. The two methods showed good agreement, but the results obtained greatly differed with the data reported in the literature.