Fruit quality and biochemical parameters, such as total phenolic content, sugars, organic acids, volatile compounds and antioxidant capacity, of six early ripening mandarin varieties ('L.A. Early, 'Okitsuwase, 'Primasol; 'Mihowase', 'Dobashi Beni' and 'Early St. Ann') were determined under Cukurova ecological conditions, Turkey. Three organic acids (citric acid, L-ascorbic and succinic acids) and three sugars (sucrose, glucose and fructose) were determined using high-performance liquid chromatography (HPLC). According to the results, citric acid was detected as the main organic acid. Sucrose was the major sugar. The highest sucrose level was found in 'Primasol' (4.54%) and the lowest in 'Okitsuwase' (3.65%). Similarly, a significant amount of L-ascorbic acid was detected in all varieties studied. Citrus juices are abundant in ascorbic acid content, which is an important antioxidant. For the total phenolic content, the amounts varied between 74.68 mg gallic acid equivalents per 100 gram (mg GAE 100 g(-1)) for 'Okitsuwase' and 83.18 mg GAE 100 g(-1) for 'Dobashi Beni'. Antioxidant activity was measured using the DPPH* assay and ranged from 68.51 to 91.01% in experimental mandarin juices.