This paper investigates the relationships between stock market returns of 13 countries based upon monthly data spanning December 1987 to April 2007. SpecifIcally, the principal component (PC) and maximum likelihood (ML) methods are used to examine any discernable patterns of stock market co-movements. Factor analysis provides evidence that stock returns in a number of Asian countries are highly correlated and, based on the resulting robust frictor loadings, they fbrm the first well-defined common factor. We also find consistent results (bused on both the PC and ML methods,) suggesting that the stock returns of all global developed economy stock markets are also highly correlated, and constitute our second factor. We conclude that, inter alia, geographical proximity and the level of economic development do matter when it comes to co-movements of stock returns and that this has important implications for financial porefolio diversification if the aim is to reduce systematic risks across countries.