A new estimation method of stochastic volatility models is proposed based on the nonparametric …lter of the instantaneous volatility process of Kristensen (2008). We use standard estimation methods for fully observed di¤usion processes but with the …ltered volatility process replacing the latent process. Our estimation strategy is applicable to both parametric and nonparametric stochastic volatility models, and we give theoretical results for both. The proposed estimators will carry biases due to the use of the …ltered volatility instead of the actual volatility, but under regularity conditions this vanishes asymptotically and our estimators inherit the asymptotic properties of the infeasible estimators based on observations of the volatility process. Our estimation strategy is applicable to both parametric and nonparametric stochastic volatility models, and we give theoretical results for both. A simulation study examines the …nite-sample properties of the proposed estimators.The authors wish to thank Professor Bruce Hansen for fruitful discussions and helpful suggestions. They also wish to thank participants at a seminar at University of Wisconsin, the CREATES opening Conference, and the 2007 EC 2 Meeting for comments and suggestions.