This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on IIAdvances in Laser Spectroscopyll the tenth course of the Europhysics School of Quantum Electronics, held under the supervision of the Quantum Electronics Division of the European Physical Society. The Institute was held at Centro "I Cappuccinill San Miniato, Tuscany, July 26, - August 7, 1981. The Europhysics School of Quantum Electronics was started in 1970 with the aim of providing instruction for young researchers and advanced students already engaged in the area of quantum elec­ tronics or wishing to switch to this area from a different back­ ground. From the onset, the School has been under the direction of Prof. F. T. Arecchi, then at the University of Pavia, now at the University of Florence, .and Dr. D. Roess of Siemens, Munich. In 1981, Prof. H. Walther, University of Munich and Max-Planck­ Institut fUr Quantenoptik joined as director. Each year the Directors choose a subject of particular interest, alternating fundamental topics with technological ones, and ask colleagues specifically competent in a given area to take the scientific responsibility for that course.