To investigate the translocation form of photo assimilates in the peanut (Arachis hypogaea L.) plant, the plants were individually supplied with 13COZ for 30 min. In the leaves, during the 13CO Z feeding period, fructose was most strongly labeled with 13C, followed by glucose, whereas a small amount of 13C was incorporated into sucrose. Within 1 d after the end of the 13CO Z feeding, the l3C abundances and 13C amounts of fructose and glucose rapidly decreased within 120 min, but increased from 120 to 240 min, and markedly decreased afterwards, while those of sucrose remained constantly low. In the petioles and stems, during the 1:3C labeling period, the 13C abundances and 13C amounts of fructose and glucose were also remarkably higher than those of other sugars and after the end of the 13CO z supply, they remained constantly higher than those of sucrose. In the leaves, a large quantity of 13C was incorporated into starch during the 13C labeling period and within 120 min after the end of the 13CO Z supply, and thereafter, rapidly metabolized. Similar results were observed for the petioles and stems. The above results indicate that the carbon currently fixed in the leaves is rapidly exported from the leaves to the petioles and stems and translocated to other parts of the plant in the forms of fructose and glucose but not sucrose, in contrast to other crops in which sucrose is the major translocation form of photoassimilates.