Biennial variation in tree diameter growth was studied during eight years (1995–2003) in nine tropical rain forests on Mt. Kinabalu, Sabah, Malaysian Borneo. These forests are located at four altitudes (700, 1700, 2700, and 3100 m.a.s.l.) on contrasting geological substrates (ultrabasic versus non-ultrabasic). The seven forests at and above 1700 m.a.s.l. may be classified as montane cloud forests, whereas the other two at 700 m.a.s.l. are lowland forests. A severe drought associated with an El Niño–Southern Oscillation event occurred from late 1997 to early 1998. Mean absolute growth rates of stem diameter in each of four 2-year periods increased from smaller (4.8–10 cm diameter) to larger (≥10 cm diameter) stems in each forest, decreased with increasing altitude on the same substrate, and were greater on non-ultrabasic than on ultrabasic substrate at the same altitudes. There were significant, concordant biennial variations in growth rates among the nine forests for both smaller and larger stems. The period of least growth included the drought in all forests for larger stems. Overall, the patterns of variation were similar among forests on different substrates at the same altitude (especially for larger stems), suggesting climatic rather than edaphic control of tree growth. Growth rates exhibited a consistent pattern in that: (i) rates for individual stems changed substantially from pre-drought (1995–1997) to drought periods (1997–1999), and (ii) the altered growth rates persisted during post-drought periods (1999–2001 and 2001–2003), especially in the montane forests. […]