Motivation for the study of the assessment of wood quality of standing trees with ultrasonic technique is both practical and theoretical. Forest managers would like to understand better how the sylvicultural practice act on wood quality. Three physiologists have known for over a century that wood quality is determined by the life conditions of standing trees. In the last decades ultrasonic methods were developed to assess wood quality of standing trees. Firstly the methods based on the increment cores type specimens bored from living trees have been developed. The measurements of ultrasonic velocities on increment cores were used for the calculation of elastic constants of wood and for the detection of the specific defects. Secondly, the techniques were developed to estimate wood quality on trees in situ, using modern computed tomographic techniques.