Banana fruit weight and size are important criteria for banana growers as they determine yield and sell prices. Within-bunch variability in fruit weight was recently shown to be related to a difference in pulp cell number (PCN) at the end of cell divisions (350 degree-day (dd) after inflorescence emergence). However, it is likely that both source activity and sink size determine fruit weight and size. Two hypotheses are tested. (i) source/sink ratio modifications during cell division phase influence PCN and thus pulp dry weight (PDW) at harvest, (ii) PCN mostly détermines fruit length while cell filling rate mostly determines fruit diameter.