Variation in flesh, flavour, sugar and acid content in F1 plants was examined in a grape breeding population. Fruit samples were harvested from individual seedling from 14 crosses. Firm, medium, and soft berries were observed from a cross of medium × medium. Medium and soft berries were frequently found from cross combination of medium × firm and firm × medium. Soft berries alone were observed between soft berries and soft ones. Flavourless progenies were frequently observed in F1 plants in a cross of flavourless × flavourless. The muscat-flavoured cultivar, 'Muscat Hamburg' has a parental potential which represents muscat-flavoured progenies in F1 plants. Foxy and special flavour progenies appeared in a ratio of 1:1 using 'Star Red' (foxy) and 'Empire State' (special) as the pollen parent, espectively. In a cross of 'Catawba'×'Muscat Hamburg', muscat-flavoured progenies were frequently observed in F1 plants. Normal distribution (mode=15.0g) was observed in the variation of sugar content in F1 plants, suggesting that there are multiple genes controlling sugar content in grapes. In particular, progenies with high sugar content were frequently found in a cross of 'Delaware'×'Muscat Hamburg'. Acid content in F1 plants was more than 0.50g when Vitis vinifera grapes were used as parents, while F1 plants with low acid content had frequently been observed when American hybrid were used as parents. In particular, progenies with low or medium acid content were frequently obtained when 'Schuyler' (early-matured) was used as the parent.