Preference tests conducted by using either clean or urine-treated paper substrates in a modified open field showed that peripheral anosmia induced by intranasal application of zinc sulphate solution eliminated the avoidance response normally shown by male mice towards an area treated with the urine of isolated male conspecifies whereas a control treatment with physiological saline resulted in the subjects displaying a marked and significant preference for the clean, untreated substrate. The present results therefore confirm that the urinary aversive factor of male mice functions through an olfactory medium. The temporary nature of zinc sulphate-induced anosmia was also confirmed in that the avoidance response to the urine of isolate males was regained between 8 and 13 days after treatment.