The objective of the paper reported herein is to determine elasticity characteristics of fruits for the evaluation of fruit firmness. The coefficient of elasticity - the ratio of the compressive stress to the deformation - was introduced to characterize the firmness of the fruit. Since the deformation is limited to a value that is below the inflection point of the stress-strain curve, this coefficient can be measured by a non-destructive method. Tests were performed with different penetrometers and good correlation was found between the coefficient of elasticity and other properties - bioyield and rupture stresses and the Young's modulus of elasticity and the coefficient of elasticity - with apple and tomato. The coefficient can be used as a good characteristic of the fruit firmness for either scientific or practical evaluation.