The paper reports the composition of some quality characteristics of five blackberry varieties ("C. Thornless", "Bursa 2", "Navaho", "Jumbo" and "Loch Ness"). Main soluble sugar and acid contents of experimental varieties were separated, identified and quantified using high-performance liquid chromatography with photo diode array spectrophotometric and refractive index detection, for organic acids, ascorbic acids and soluble sugars, respectively. According to the results, malic acid was detected as the main organic acid while citric acid was not detected in blackberry fruits. Ascorbic acid content was found very low quantity and also was not detected in all the cultivars. As for the sugars, fructose was found as the most abundant sugar and highly detected in "Navaho". However, the highest total sugar/malic acid ratio was found in cv. C. Thornless. (c) 2005 Elsevier Ltd. All rights reserved.