Efficient Method of Moments is used to estimate and test continuous-time diffusion models for stock returns and interest rates.For stock returns, a four-state, two-factor diffusion with one state observed can account for the dynamics of the daily return onthe S&P Composite Index, 1927–1987.This contrasts with results indicating that discrete-time, stochastic volatility models cannot explain these dynamics.For interest rates, a trivariate Yield-Factor Model is estimated from weekly, 1962–1995, Treasury rates.The Yield-Factor Model is sharply rejected, although extensions permitting convexities in the local variance come closer to fitting the data.