The fabrication and characterization of odor sensors based on molecularly imprinted polymers is reported as the first case of imprinting formaldehyde. A quartz crystal microbalance is employed as a sensitive apparatus of a sensor for the determination of odor formaldehyde. An equation is deduced to characterize the interaction between molecularly imprinted films and the template. A linear relationship between the frequency shifts and the concentration of analyte in the range of 1.25 to 14.25 mu M is found. The detection limit is about 20.5 mu M. The sensor can selectively distinguish gaseous formaldehyde. It is envisaged that this novel and handy method could be employed to determine formaldehyde gas in the atmosphere. (c) 2004 Elsevier Inc. All rights reserved.