The wide use of the laser and light therapy allows to accumulate the huge practical material on application of the low-level electromagnetic field effect in various medicine spheres. We are going to clarify the prima facie seeming contradictory experimental observations as most of them may be explained by the field model, which treats the registered effects as a field disturbance of human organism in a low level electromagnetic radiation of optic band that is an alteration of its inner structure on cell, sub-cell and organ levels. The current investigations show that refraction index and scattering properties of biological liquid and tissue are changing in a low level laser field due to the alteration of their structure state. The field model of the low-level optical radiation effect on a human organism is presented. In vivo and in vitro experimental results confirm this approach. Thus, the field effect mechanism is the main one that is responsible for the alteration of the bioliquid structure and the positive effect of the laser and light therapy treating