Residential thermal conditions are important because people spend the majority of their time in the home environment. Indoor temperature and relative humidity(RH) were measured continuously over 1 year in 14 residences in Seoul, Korea. The relationship between residential indoor and outdoor conditions were determined by four meteorological parameters-temperature, apparent temperature(AT), RH, and absolute humidity(AH). Outdoor and indoor temperature, AT and AH were closely correlated, but RH was not. While indoor temperatures, AT, and AH were significantly higher than the corresponding outdoor levels, indoor RH was significantly lower than outdoor RH. Regression models between indoor and outdoor temperature detected a heating threshold at 15.0oC of outdoor temperature. The indoor thermal conditions were significantly different by the two residence types. Indoor temperatures in apartments were lower in summer and higher in winter than those in detached houses. However, indoor RHs in apartments were lower than in detached houses. During tropical nights, the daily temperature range was higher in residences with air-conditioning than in naturally ventilated residences. Keywords : Indoor temperature, Indoor relative humidity, Thermal comfort, Residence type, Air conditioning, Season