Mice were treated on active avoidance to determine the effect of cholinergic and anticholinergic drugs on retention. All drugs were administered intraventricularly after training and one week prior to testing retention. A dose-response curve was determined for each drug. The results indicate that each of 6 anticholinergics impaired retention. The 8 cholinergic drugs tested all yielded U-shaped dose-response curves with controls showing poor retention, low doses of the drugs yielding good retention and high doses resulting in poor retention.