This is to describe the housing situation of Hanoi, Vietnam, after the introduction of market economy under the socialist regime. Under the current situation, there are two types of houses: one is the pencil-houses, relatively large and privately owned, and the other is the apartment units, small and rented from the government. There is a large gap between these two alternatives. The former is popular but the efficiency of ventilation and consequently, the living condition varies under the weak control of building regulation. People in the latter require more space and extension is often undertaken. It is necessary to control the situation for the improvement of the dwelling condition.