Some studies indicate that correlations between GDP growth in Japan and in emerging East Asian countries are consistently positive; others claim that such correlations are consistently negative. In this analysis of 10 East Asian countries over 1975–2002 using quarterly GDP data, a Markov-switching vector autoregressive system with three growth cycle regimes is used to examine to what extent such correlations are sensitive to third-country effects, transmission mechanisms, and the quality of Japanese output data. After controlling for third-country effects, correlations with Japan are found to be almost uniformly negative. When transmission variables are taken into account, however, positive correlations appear during rapid-growth regimes for China, Malaysia, Singapore, Taiwan, and South Korea. When higher-quality Japanese output data are used, shocks in these countries are symmetric with Japan's disturbances in growth-recession and rapid-growth regimes. However, synchronization with Japan is never present in the normal-growth regime. Because these five countries are not fully synchronized with Japan, it is probably premature for them to engage in exchange rate arrangements involving the yen.