The contents of reduced and total ascorbic acid, vitamins P, reducing and total sugar, citric acid, ash, calcium, crude fibre and moisture in the edible portions of 23 main varieties of Chinese oranges and tangerines have been determined. The change of ascorbic acid content of the fruits during storage has also been investigated.Ascorbic acid content of orange is higher than that of tangerine. Oranges contain 46.6-62.3mg% of reduced ascorbic acid and 48.8-72.4mg% of total ascorbic acid and tangerines contain 14.3-48.7rng% and 19.5-50.7mg% respectively.Locality affects the composition of fruits: fruits grown in Fukien and Kwangtung provinces generally contain more ascorbic acid and .sugar, and less citric acid and calcium than those grown in Kianghsi and Chekiang.Five strains of fruits have been subjected for storage test. The loss of ascorbic acid in the fruits during 2-3 months storage in the winter season ranged 0-40% of the original content. No loss of ascorbic acid has been observed in Hsuehkan (雪柑), after 3 months storage at -2? to 4℃, but loss of 40% of the reduced and 20% of the total ascorbic acid content occurred in Kwangtung chiaokan (广东蕉柑) after two and half months storage muler -1? to 12℃