Processes involving heat transfer from a humid air stream to a vertical plate, with simultaneous deposition of frost, are of great importance in a variety of refrigeration equipment. In this work, frost growth on a vertical plate in free convection has been experimentally investigated. The plate, cooled by the internal circulation of glycol, was placed in a vertical channel open at the top and bottom in order to permit the natural circulation of ambient air. The cold plate temperatures were varied in the 13 to 4°C range, while the relative humidity and temperature of the ambient air were taken in the 31-58% and 26-28°C ranges, respectively. Measured quantities (frost thickness, frost surface temperature, deposited mass of frost, heat flux at the plate/frost interface) were compared with results given by a simple model based on standard relationships (for heat and mass transfer coefficients, frost density and thermal conductivity) reported in the literature.