Southeast Asian equatorial tropical rain forests are characterized by a humid climate without distinct seasonality in monthly temperature and rainfall. Whether rain-forest trees have distinct annual patterns in vegetative and reproductive activities has not been well studied. We analyzed the periodicity of vegetative and reproductive activities of rain-forest trees using the temporal patterns of litterfall along elevation and soil-nutrient gradients on Mount Kinabalu, Borneo. Fine litterfall was collected every two weeks from Feb. 1996 until Mar. 2006 in nine sites, which were placed in a matrix of four elevations (700, 1700, 2700 and 3100 m) and two soil types of contrasting phosphorus availabilities. Collected litterfall was oven-dried and sorted to leaf, reproductive-organ, twig, epiphyte and dust fractions. We applied a Fourier analysis to the time-series data of each litter fraction. Leaf litterfall demonstrated distinct annual periodicity (approximately 360-day cycle) in all forests. Reproductive-organ litterfall demonstrated annual periodicity in one montane forest, but much weaker periodicity with longer cycles in the other forests. This suggests a distinct climatic cue to induce the vegetative annual cycle, which is independent from reproduction. We will discuss the periodicity of reproductive activities in relation to soil nutrient availabilities.