Abstract
Most investment decisions focus on a forecast of future events that is either explicit or implicit. Generally asset pricing models postulate a positive relationship between a stock portfolio’s expected returns and risk, which is often modelled by the variance of the asset price. The essence of this paper is to use GARCH in mean and EGARCH to examine the relationship between mean returns on the Nigeria commercial banks portfolio investments and its conditional variance or standard deviation. After estimating a variety of models from Central Bank of Nigeria Statistical Bulletin 2010 data, we found out that using the GARCH in mean a positive and significant relationship exist between commercial bank portfolio return and volatility, while the EGARCH model gives a negative relationship. We suggest that market operators should try as much as possible to prevent avoidable bad news.