Male hooded rats were conditioned in one trial to avoid saccharin by pairing saccharin drinking with an intragastric injection of LiC1. A 24 hr water-saccharin preference test showed that conditioned rats exhibited a very low preference for saccharin whereas rats injected intraventricularly with cycloheximide (CXM, 400 mug) 5, 7, or 9 hr before training exhibited a greatly increased saccharin preference which differed significantly from NaC1 injected controls. This 24 hr amnesia was found to be dependent upon the time of administration of CXM, since injection at 1, 3 or 17 hr before training did not confer amnesia. The nature of the task, a control measure and a control experiment indicate that the CXM-induced change in saccharin preference at 24 hr is not due to a CXM-induced aversion, nor a loss in drinking ability nor an inability to retrieve information whilst under the influence of CXM.