This chapter provides a chronological development of randomized response techniques for quantitative sensitive variables. The methods of estimation of the population mean, variance, and unbiased estimator of the variance are proposed under the SRSWR sampling scheme. Details of Greenberg et al., (Journal of the American Statistical Association. 66:243–250, 1971), Eriksson, (International Statistical Review. 48:29–32, 1973), Godambe, (International Statistical Review. 48:29–32, 1980), the additive model of Poole, (Journal of the American Statistical Association 69:1002–1005, 1974), the product model of Pollock and Bek, (Journal of the American Statistical Association 71:884–886, 1976), Eichhorn and Hayre’s (1989) model, the distributive model, among others, are discussed. The general RR model proposed by Arnab, (Communications in Statistics e Theory and Methods 19:3751–3757, 1990), along with the method of estimation of population characteristics, is presented. It is also demonstrated that almost all the qualitative and quantitative RR models can be obtained as special cases of Arnab, (Communications in Statistics e Theory and Methods 19:3751–3757, 1990) model.