Microorganisms associated with deterioration of banana fruits (Musa sapientum and Musa acuminata var. dwarf Cavendish) were isolated. Rhizoctonia solani was isolated from the M. acuminata var dwarf Cavendish while Aspergillus niger was isolated from M. sapientum. Bacteria isolated were Streptococcus pyogenes and Proteus vulgaris (from M. acuminata var. dwarf Cavendish) and Alcaligenes faecalis and Streptococcus faecalis were isolated from M. sapientum. The mean proximate composition of M. sapientum on the fifth day of storage gave a decrease in the carbohydrate (18.807 to 5.334%) and lipid (3.475 to 2.852%) contents while an increase was observed in the moisture (73.919 to 85.425%), protein (1.375 to 1.554%) and ash (1.008 to 2.431%) contents. The mean proximate composition of Musa acuminata var. dwarf Cavendish on the fifth day of storage gave a decrease in the carbohydrate (16.919 to 8.334%) and lipid (3.292 to 2.874%) contents while an increase was observed in the moisture (75.493 to 81.987%), protein (1.713 to 1.947%) and ash (1.937 to 1.969%) contents. The fruits were stored in different ways. The results obtained showed that fruits stored at 4oC±1 (in a refrigerator) gave a longer time before initiation of ripening (20 days) compared with fruit stored in moist sawdust (7 days) and fruits stored in polythene bag moistened with KMn04 solution (3 days). The rate of deterioration of the fruits was also examined. Fruits stored in moist sawdust gave no sign of deterioration throughout the course of storage (31 days). Fruits stored at 4oC±1 were contaminated with mold on the 10th day. Fruits stored in polythene bag moistened with KMn04 solution became contaminated on the 7th day and the control, 8th day. The results of this work show that refrigeration (4oC±1) appeared to be the most appropriate condition for prolonging the initiation of ripening of banana varieties used while moist sawdust appeared to be most suitable for improving the shelf life of the banana fruits.