Nitrous oxide (N2O) is both a greenhouse gas and a catalyst of stratospheric ozone depletion. Of the emissions associated with human activity, 50% come from agriculture (Nakicenovic and Swart, 2001). In many terrestrial systems, 50% (Rover, 1988) to 66% (Duxbury, 1982) of N2O emissions occur in late winter/early spring during cycles in which the soil freezes and thaws. The phenomenon of N2O peaks during freeze-thaw cycles has been attributed to a flush in available carbon substrate for microbial metabolism coupled with anaerobic conditions inducing denitrification (Firestone, 1980). However, this may be only part of the explanation. Using laboratory simulations, Sharma et al. (2006) found that freeze-thaw cycles resulted in a change of denitrifier community composition. This change included very low or no expression of the nosZ gene coinciding with increased N2O fluxes. My study examines the effect of differing freeze-thaw intensities in the field on the presence and activity of the nosZ gene in denitrifying microbial communities and further relates these findings to corresponding N2O emissions.