This study explores taxation literature and uses empirical evidence from the period of 1996-2006 to examine tax competition and tax harmonization in Southeast Asia. The study seeks evidence for the existence of tax competition by analyzing recent trends in two groups of measures of taxation: tax rates and tax revenues. Evidence is found for a decline in statutory corporate tax rates, developments commensurate with the existence of tax competition. On the contrary, the tax revenue data presented here, show that the expected decline in total tax revenues has not occurred; indeed, a significant increase has been recorded. It is also supported by empirical evidence of the ratio of corporate tax revenue either relative to GDP or to total tax revenue. The two groups of measures of taxation thus provide apparently inconsistent views of the impact of tax competition. There follows an analysis of the elements of tax competition according to literature, in an attempt to draw out its implications for the experience within the Southeast Asian region. This study also examines the case for tax harmonisation and the Southeast Asian experience.