This document is the result of a four-month project to update the DYNAMITE model which simulates water and nutrient cycling in tropical forests. The model DYNAMITE was developed within the framework of a special study and described in Tropenbos Series 4. The model includes improved concepts concerning relevant soil and vegetation processes, which are included on a diskette. The updated version of the model is also user-friendlier, as the structure, accessibility and surveyability of the computer programme have been improved. The nutrient part of the model has been submitted to a sensitivity analysis to obtain insight into the relative importance of the various model-input parameters. It appeared that some input parameters that have the strongest effect on wood growth are very difficult to determine. This obviously remains a week point in modelling the growth of tropical forests. This document is meant to accompany the model description in Tropenbos Series 4.