The emergence of capital markets in Asia and South America, the relaxation of foreign capital controls and the adoption of flexible exchange rate regimes has prompted heavy cross-border investments in recent years.  Simultaneously, volatility in these foreign exchange markets has increased, leading to increased risk following the adoption of these flexible exchange regimes.  As such, investors have become more interested in knowing what impact the volatile markets have on their investments.  This, they seek to know, through the returns on their stock investments as stock prices are said to be a representation of firm value.   This thesis uses firm size as a parameter to analyse the role of macroeconomic variables with emphasis on  exchange rate variability on stock returns using data from 67 Swedish companies listed on the Stockholm stock exchange and selected from all the three market capitalization segments (large cap, mid cap and small cap) according to the OMX index classification. We used returns from all the non-financial firms listed on the Stockholm stock exchange between the years 1997 to 2009.  Based on the Arbitrage Pricing Theory, and using multiple regression model, we sought to ascertain  if the effect of movements in the SEK/USD and SEK/Euro exchange rates are different for companies of the small, mid and large capitalizations segments of the OMX Stockholm stock exchange and which other control variables will influence these returns more than the exchange rate movements.   Using bilateral monthly exchange rates for the USD and Euro, we find that 55 out of the 67 companies are significantly exposed to exchange rate changes within all the segments.  These are almost evenly distributed relatively across all the capitalization segments though the absolute numbers may differ considerably.  We further use one-way ANOVA to find out if there are any differences in the means of the exposures of the companies in the respective segments.  Still, we find no significant difference in their means.  These therefore give little evidence to conclude that there is actually a difference in the exposure of firms in the respective capitalisation segments to exchange variations.  We also discover that apart from exchange rate variations, other macroeconomic variables also play a big role in determining the returns of the stocks of firms.