Strength evaluation of structural elements has been done by nondestructive methods, using ultrasonic pulse velocity, hammer rebound, and localized pressure, either individually or in a combined way. The effects of the mineralogical composition of the coarse aggregate, moisture content, and age of concrete on pulse velocity and rebound number is reported. Standard cylindrical specimens cured at 100% relative humidity were tested for compressive strength. Regression equations thus obtained were used to estimate the in-situ compressive strength of reinforced prisms (0.15 by 0.15 by 1.00 m). The prediction error is calculated from the comparison of the estimated strength and the strength determined on drilled cores.