Hong Kong is a densely populated Asian city with a monsoon-influenced humid subtropical climate that experiences a pronounced urban heat island (UHI). During the summer months conditions in Hong Kong are generally hot and humid and can get quite oppressive. The added burden of the UHI on these conditions can have human health and thermal comfort consequences, alter the city's photochemistry and affect urban air pollution and affect the energy consumption needs of a city through impacts on cooling. To investigate the UHI in Hong Kong, vehicle based temperature and relative humidity traverses were used to determine spatial differences in the summertime UHI across the city. A total of 29 vehicles traverses were undertaken during the coolest and/or hottest part of the day across eight days during May-June 2008. This presentation will investigate spatial variability of urban heat island effects in the most urbanized areas of Hong Kong. GIS resources were used to identify land-use and surface characteristics surrounding each of the traverse measurements and the characteristics associated with peaks in both simple air temperature UHI intensity and UHI intensity associated with thermal comfort indices will be discussed. The hottest regions within the Hong Kong urban area are often associated with areas of extremely high population density; therefore the issue of exposure to the UHI will be discussed. Socio-economic/demographic data at the tertiary planning level from the latest Hong Kong census will be used to quantify exposure to urban heat island magnitude among different Hong Kong resident populations.