In this paper, the degree of export rivalry or competition among China and ASEAN-4 (Malaysia, Singapore, Thailand and Indonesia) is examined using the shift-share methodology. Our results show that overall China was more competitive than ASEAN-4 in its exports to the US. China was more competitive in manufacturing exports whereas ASEAN-4 fared better in agricultural or primary exports. China's advantages in export growth and industry structure vis-à-vis ASEAN-4 were less pronounced before, than after, the onset of the Asian financial crisis, implying that the crisis has indeed affected ASEAN-4 more than China. It has been contended that China's advantage in manufacturing exports could have been accentuated by Hong Kong' production in South China, which has been counted in US trade statistics as China's exports to the US. After disentangling Hong Kong's production in China, the degree of rivalry between China and ASEAN-4 is significantly reduced. Our analysis points to the role of sub-regional production synergy in boosting a country''s export competitiveness.