Compressive strength of concrete is widely accepted as a characteristic property indicating and representing its quality. The accuracy of both ultrasonic and mechanical strength is discussed and the advantages of ultrasonic testing are pointed out. Measurements of ultrasonic pulse velocity and mechanical crushing load of concrete cubes made from the aggregate and cement used in the State of Qatar are reported in this paper. Measurements on concrete cores from a local structure are also reported. The results are compared with previously published correlation between the velocity and mechanical strength of concrete.