During storage conditions banana fruits get infected by several fungal diseases like finger rot, fruit rot, crown rot, cigar-end rot and pitting disease etc. Among these diseases fruit rot caused by Lasiodiplodia theobromae [(Path.)Griff. and Maubl.] is most serious post harvest disease under South Gujarat condition and it causes changes in biochemical contents of banana pulp and peel during ripening. Sugar, Phenols Phenylalanine ammonia lyase (PAL), Polyphenol oxidase (PPO) and Peroxidase (POX) are said to play important role in plant disease resistance. Total sugar, phenolic content, phenylalanine-ammonia lyase, polyphenol oxidase and peroxidase activities were determined in infected and uninfected banana fruits during ripening at 0, 48, and 72 h after incubation. The results showed that total soluble sugar content was increased with the ripening stages but it was decreased in infected fruits as compared to uninfected fruit. Reduction in PAL activity and enhancement in PPO and POX activity may be correlated with reduction of phenol content during ripening stage but it was still increased in infected banana fruits.