Climate change issues and building energy use implications in subtropical Hong Kong were examined. A total of 40 years (1961-2000) of measured hourly temperature data were gathered and analysed. Three different parameters were examined, namely mean temperature, cumulative frequency of occurrence and cooling degree days (CDD). It was found that there was an underlying trend of temperature rise in recent years. Such temperature increase tended to occur more frequently during the winter period and mid-season than the summer months. The slight increase in CDD during the last 20 years suggested that cooling requirements and, hence, energy use for air conditioning might be affected if the trend persisted. The frequency of occurrence analysis, however, revealed no significant changes in the outdoor design conditions, and peak building cooling loads were expected to remain unchanged. This paper presents the work and discusses the energy use implications. (C) 2003 Elsevier Ltd. All rights reserved.