The influence of controlling temperature during apple (Malus domestica Borkh.) maturation on sugars, fruit maturity, and watercore occurrence was investigated in watercore-susceptible `Himekami' and `Fuji' apples. The incidence of watercore at 13/5 and 23/15C was greater than at 33/25C or ambient temperatures in `Himekami' apples in 1991 and was greater at 18/10C than at other temperatures in `Fuji' apples in 1990. In 1992, the extent of watercore increased as fruit temperature decreased from 28 to 14C and 23 to 9C in `Himekami' and `Fuji' apples, respectively. Watercore occurrence affected by fruit temperature was not related to fruit maturity, as judged by ethylene evolution. The effect of fruit temperature on sorbitol was relatively small compared with that on other sugars, and no relationship was found between watercore development and sugars. These results suggest that fruit temperature affects watercore expression independently of fruit maturity or sorbitol metabolism in the fruit in watercore-susceptible apple cultivars.