This research is an analysis of the underlying factors that influenced Malaysia-Singapore relations during the watershed period of Mahathir Mohamad as the Prime Minister of Malaysia (1981-2003). The study proposes that the bilateral tensions between Malaysia and Singapore were, to a large extent, affected by such things as the burden of historical baggage from their acrimonious parting in 1965, after a short period of unification; the differences between them in their perceptions and approaches in handling bilateral relations; and their political cultures and the leadership styles of their prime ministers, but for the purposes of the present study, specifically those of Mahathir and Lee Kuan Yew. Despite the strong underlying differences, ...