Persimmon fruit possesses relatively large calyx lobes compared with other fruits. Unlike fruit skin, persimmon calyx lobes have many stomata on their surface and retain chlorophyll until harvest. So, photosynthesis by calyx lobes may have some contribution to fruit development. To examine this possibility, 13CO2 feeding experiments were conducted at an early stage of fruit development. The calyx lobes showed the greatest photosynthetic ability among fruit parts, and accounted for almost all of fruit photosynthesis. The photosynthetic activity of calyx lobes expressed on unit area basis was about 140 % of that of leaves. However, most of the 13C-assimilates in calyx lobes did not move to other parts and stayed there even 10 days after feeding. Moreover, covering calyx lobes with aluminum foil on the tree had no significant effect on fruit set and fruit growth, despite a remarkable decline in fruit photosynthesis. These results indicate that photosynthesis by calyx lobes has no contribution to early fruit development.