Cities in developing countries are growing ever larger and more dense, fostering congested household environments. Using data from Bangkok, this paper examines the effect of household crowding on multiple measures of family relations, looking at the possible ''social costs.'' The data show that objective household crowding does increase marital instability and arguments, and parent-child tensions. Subjective household crowding affects not only these three aspects of family relations, but also results in more frequent disciplining of children. These effects are largely mediated by psychological stress. The paper rejects the argument that subjective crowding is an effect, rather than a cause, of marital and family relations, and shows little difference between wives' and husbands' reactions to crowding. The consequences of household crowding, generally found to be selective and modest in North America and Europe, are stronger in Bangkok, a city with crowded conditions more typical of less developed nations.