In order to clarify the long-term variability of the wind in complex terrain, an investigation was conducted on Jeju Island, Korea. The four coastal areas and the three mountainous areas were selected and wind data for 8-11 years from meteorological observatories were collected for this work. Inter-annual variations, monthly variations and diurnal variations in wind characteristics were calculated from the long-term wind data. As a result, it was found that wind speed is higher in the winter season while it is lower in the summer season. Wind at all sites blew strongly in the daytime and weakly at night. Also, wind energy and the range of variation in wind energy varied significantly from region to region on Jeju Island. Inter-annual variations in wind energy on Jeju Island occurred a little greater than seen in the results of earlier works conducted in other place. Copyright (C) 2009 John Wiley & Sons, Ltd.