It is well known that the OLS estimator, though unbiased, is inefficient in the presence of autocorrelated disturbances. Further, it is also widely accepted that C-0 (Cochrane-Orcutt) estimator is more efficient than OLS estimator. However, Kadiyala (1968) and Maeshiro (1976, 1978) have argued that OLS is more efficient than C-0 when the independent variable is trended and the autocorrelat ion coefficient is positive. We re-examine this issue and show that C-0 is more efficient than OLS for the model without an intercept term.