Stress-relaxation analysis was applied to examine tissue softening in tomato fruit using a conical probe. Next, the technique was applied to banana using an instrument capable of controlling the plunging depth. When bananas were ripened in a biotron at 25°C, index of peel color increased after the burst of ethylene production, while moisture and cellulose contents did not change during ripening. Next, bananas were ripened with ethylene during 4 days. Changes in the mechanical properties of pulp were detected by a stress-relaxation method, suggesting that the decreases in elasticity and viscosity of the pulp are major physical components of pulp softening. Results of chemical analysis clearly revealed that the partial breakdown characterized by a decrease in arabinose, mannose and galactose contents in the hemicelluloses of the cell wall preceded the breakdown of starch. These observations suggested that the associated process whereby the contents of pectic and hemicellulosic polysaccharides and starch decreased is the main cause for the pulp softening process. In plantains (cooking banana) the physical and chemical properties were analyzed during fruit softening. The results obtained suggest that cell wall polysaccharides, pectin and hemicelluloses are the chemical components responsible for the changes in firmness rather than starch in plantain pulp.