The neural mechanisms underlying the perception of complex odor mixtures are largely unknown. The present study investigated the hypothesis that odorants in a mixture are processed and perceived in series. The results indicate that (i) odorants in mixtures are temporally processed with up to several hundred milliseconds separating individual components; (ii) 'fast' odorants are more likely to be a suppressor of 'slow' odorants than the reverse; and (iii) separation times can be altered by changing the concentrations of mixture components. These findings provide a new mechanism to account for the limited ability of humans to identify odorants in mixtures and for odor suppression.