This book deals with the issue of quality adjustment in price indices. Indeed, traditional indices such as Laspeyres do not allow to take into account in the measurement of price changes, changes that are due to the quality adjustment. However, the hedonic method intervenes to deal with this measurement problem, by making it possible to take into account the quality adjustment (introduction of a new product on the market, replacement or disappearance of a product) in the calculation of the price index. The empirical validation of our analysis shows that the hedonic index increases more slowly or decreases more quickly than the classic Laspeyres index, this is mainly due to the consideration of the quality adjustment in the measurement of the evolution of price.