This chapter presents a survey of applications of the Hanle effect to atomic physics. Emphasis is placed on the variety of phenomena studied, rather than on a complete survey of data obtained. If we take, for example, one of the classical applications of the Hanle effect, lifetime measurements, the discussion of all results obtained would fill a chapter of this book by itself. A concise survey of its abundant applications seems more useful at this point, all the more so since especially in connection with laser experiments new and exciting results have recently been obtained and new possibilities opened up. Examples of these are observation of squeezing, effects in connection with the correlated emission laser or applications in nonlinear optics. The more classical uses of the Hanle effect are described in previous reviews, e.g., Happer and Gupta,(1) Pokozan’ev and Skrotskii,(2) and Chaika.(3)