The CAPM’s prediction for the intercept is that it should equal zero and the slope should equal the excess returns on the market portfolio. The results of the study refute the above hypothesis about the slope and offer evidence against the CAPM for all the sub-period and even for the whole period. The tests conducted to examine the nonlinearity of the relationship between return and betas support the hypothesis that the expected return-beta relationship is linear. Additionally, this paper investigates whether the CAPM adequately captures all-important determinants of returns including the residual variance of stocks.The results demonstrate that residual risk has no effect on the expected returns of stocks for the whole period and the entire sub –periods except for the last period of 2003-2008 which shows that returns are affected by non-systematic risks during that specific period, justifying the fact that the operating activities of the firms have an impact on their stocks returns