The book describes the basic laws of radiation propagation through transparent light guides of various designs: straight and curved, with a constant and variable section along the beam, with straight and oblique ends, round and layer. The method of calculation of light transmission by light guides of conical beams of rays considering the main sources of light loss is given. The results of experimental studies of transparent light guides are given: indicators of their scattering, light distribution and depolarization, light transmission. Particular attention is paid to the study of transparent light guides for the transmission of forced solar radiation. When writing the book, original theoretical and experimental studies of the authors were used. The book is intended for scientific and engineering workers involved in the field of optical-mechanical, electronic-optical and lighting instrumentation.