The objective of the experiments in this study was to investigate the proposed aversive stimulus properties of scopolamine hydrobromide (1.2 mg/kg I.P.) All research designs were based on the respondent condit­ ioning paradigm. In Experiment I, scopolamine was used as a (putative) aversive UCS in order to produce condit­ ioned suppression of licking to a light CS. No evidence of suppression was found.It was proposed that this may have been due to the inability of the UCS itself to suppress responding. In a second experiment, scopolamine injections were paired with one side of a shuttlebox, and saline injections were paired with the other side. Subsequent free choice tests yielded a constant prefer- ence for the saline associated side. In a further test where subjects were injected 20 minutes prior to confine­ ment, no avoidance of the scopolamine associated side was observed.These results suggest that the onset of scopolamine effect is aversive.