The paper reports a spectrophotometric methodology to determine the anthocyanin content in blood orange juices. The criterion of differenceof absorbances at 510 nm in two aqueous solutions (pH 1 and pH 4.5) revealed the real concentration of free anthocyanins, using an absorption coefficient obtained from the purest cyanidin-3-glucoside standard. The quantity of pigments is expressed as concentration of cyanidin-3-glucoside, the most important anthyanin in blood orange juices. The method was applied to fresh and concentrated processed juices and was controlled by HPLC anthocyanin analysis in the same juices.