Blossom-end rot (BER) is a physiological disorder that produces rotting in the distal part of the fruit. Is it thought that blossom-end rot is a calcium deficiency related disorder. However, A lot of factors have been linked to the incidence of this disorder. BER sets in the fruit during stages of high fruit expansion phase. In the present work, we study calcium concentrations and amounts in bell pepper fruits at different fruit sections and different developmental stages. Additionally, expression of EXPANSINA was determined to identify the fruit developmental stage where fruit expansion is higher to be related to the set of BER