About half of the South Korean population lives in the three major metropolitan areas, which are Seoul, Kyeonggi and Incheon. Among this group, more than 50% live in apartments. In this study, the relationship between the concentration of indoor VOCs and environmental factors was investigated in metropolitan apartments in the occupation stage. The maximum concentration of TVOC (total volatile organic compounds) was monitored in spring season. Among the identified VOCs, toluene was present in the highest amount, followed by terpene, aldehyde and hydrocarbon. Due to the specific indoor sources, the I/O ratio of terpene (e.g. d-limonene, α-pinene, and β-pinene) was relatively higher than that of the others. The construction year and length of residence were revealed as the environmental factors having the greatest influence on the concentration of indoor benzene, toluene, ethylbenzene, xylene, styrene and hydrocarbon, and the relationship was statistically significant. The floor and size of the apartment influenced the levels of indoor nonanal. The relationships between individual VOCs showed highly positive correlations that are statistically significant. Through the relationship study, it was found that factors including newly built apartment, short period of time after moving in, high floors and small floor area were the main factors inducing an increased concentration of indoor VOCs in apartments. Keywords : Apartments, Environmental factor, Indoor air quality, Volatile organic compounds