SERRISTE is a decision support system providing suitable climatic setpoints for the production of greenhouse tomatoes. The system is based on an analysis of the practices as they can be defined by expert growers and agronomists, and expressed as a set of constraints. The most significant ones links the day and night temperatures to the forecasted solar radiation, to balance the rates of growth and development with that of the photosynthesis. Additional physical knowledge is used to determine the necessary set-points from the goal mean temperatures. SERRISTE has been tested in southern and western France in extension services and has proven its capability to ensure a good if not better production at a lower cost.