This paper examines equity market linkages in the Pacific Basin (PB) region and their relations to other mature markets and also assesses the response of these markets to major global events. Results from weekly data for market pairs and for the region as a whole consistently suggest that markets in the PB region are internally interdependent and exhibit significant external relations mainly with the US (rather than Japan). The presence of potent market linkages seems inconsistent with market efficiency provided that implied trading rules yield risk-adjusted excess returns. However, the results further indicate that PB market linkages, both internally within the region and externally with the US, have endured considerable weaknesses particularly since the September 11, 2001 terrorist attack. Such recent weakening of equity market linkages may have strengthened diversification benefits available to US investors from investing in the PB region. We also obtain evidence indicating that three main factors significantly explain the differing degrees of market linkages across countries in the PB region; namely, exchange-rate volatility, equity market volatility and money-market interlink.