In order to study the drying of red pepper in open sun and greenhouse conditions drying experiments at constant laboratory conditions and at varying outdoor conditions were carried out. Laboratory drying experiments were undertaken, inside a wind tunnel where solar radiation was simulated by a 1000 W lamp, for different external parameters (incident radiation, ambient temperature and air velocity). Effect of drying parameters on moisture content and drying time were determined. A simple drying model of red pepper related to water evaporation process was developed and verified. Outdoor drying experiments were carried out in open sun and greenhouse conditions respectively to validate the drying model obtained at laboratory under constant conditions. It was found that the laboratory model overestimates the drying process under time varying conditions. A correction factor was then introduced in the formulation of the model to adjust these predictions. In studying the consistency of the model coefficient of determination and reduced chi-square were used. The results of these tests have confirmed the consistency of the model at laboratory under constant conditions and in open sun and greenhouse conditions. (c) 2006 Elsevier Ltd. All rights reserved.