An experimental external external collector type, solar dehumidification dryer was retrofitted with a simple computer-based control system. Solar, solar-dehumidification, and air-drying of 3cm-thick douglas-fir were carried out to investigate the drying-conditions and characteristics of this system, and to analyze the energy efficiencies of each drying met hods in summer. The drying rate of solar-dehumidification was 12%/day, which was about 2 times and 3 times faster than that of solar-and air-drying, respectively. The amount of diurnal temperature fluctuation inside the solar-dryer was greatly reduced and the energy efficiency was enhanced from 25% to 60% by the dehumidifier.