Suspension cells of carrot plants grown on mixed carbon sources of glucos (Glc) and malate preferentially used Glc. The cells started to utilize malate only after Glc was depleted from the medium, thus exhibiting a diauxic growth. Theresidual concentration of Glc decreased rapidly during the first growth phase, and that of malate decreased only during the second growth phase. Malate uptake was negligible throughout the diauxic growth, suggesting that malate was being utilized via another metabolite. An active metabolic flow from fumarate to pyruvate and oxaloacetate via malate was induced in cells during the second growth phase. These results strongly suggested that malate remained unused in the medim in the first phase, and in the second phase it was converted extracellularly into fumarate, which was subsequently transported into cells and metabolized into malate and further into pyruvate and oxaloacetate. This study presents the second case of diauxic growth in plants and the peculiar mode of malate utilization.