The results obtained in recent years on laser irradiance propagation in random weakly inhomogeneous media with large scale index of refraction fluctuations are reviewed. Of particular concern are the problems of the cozrelation theory of fluctuations of irradiance propagating over large distances, where the effects of multiple scattering are greatly pronounced. Much attention is paid to the results on laser beams spread and phase fluctuations. Consideration is given to problem of the study of spatial spikes of irradiance that had passed through a turbulent media; which is comparatively new but important for practical applications. Systematic comparison of the theory with experiment is given where appropriate. The methods of analyses reviewed in this paper are applicable to a class of stochastic and dynamic partial differential equations and thus may be of interest in other areas of engineering reseach.