This study aims to describe the time course of non-structural carbohydrates concentration in mature leaves of peach seedlings (cv GF 305) during the night. It was observed that the rate of starch breakdown was constant all through the night. This breakdown allowed to maintain the pool of exportable carbon until the beginning of the next photoperiod. The rate of carbon export decreased throughout the night and was close to the rate of starch breakdown at the end of the dark period. The sorbitol to sucrose ratio (SSR) changed little throughout the night. The kinetic characteristics of sorbitol and sucrose synthesis and exportation are probably central points of the SSR behavior. The apparent exportation rates of sorbitol and sucrose were calculated.