The concentrations of formaldehyde, individual volatile organic compounds (VOCs) and total VOCs (TVOC) were measured in four new manufactured houses on three occasions over nine months following construction. Ventilation rates were also measured. A mass-balance model was used to calculate area-specific emission rates of the target analytes. Formaldehyde concentrations were all less than a guideline value of 50 ppb. One-half of the 58 target VOCs had median concentrations at or below 1 ppb. The most abundant VOCs were terpene hydrocarbons, ethylene glycol, hexanal, 2-butanone and acetic acid. Concentrations of hexanal, other aldehydes and acetic acid often exceeded their odor thresholds. The median TVOC concentration was 1.6 mg m-3. In general, there were no large decreases in the emission rates of individual VOCs or TVOC over the course of the study. The data suggested that wood products were a dominant source of VOCs in all houses.