The conditions under which neophobia and enhanced neophobia occur in the albino rat were studied. Neophobia to a .1% saccharin solution was demonstrated in a 10-min single-bottle test. This neophobia was enhanced by pairing water ingestion with a radiation exposure of 100 r. or an injection of lithium chloride 24 hr prior to the saccharin test. In addition, it was found that the differences in consumption of saccharin in a 10-min single-bottle test due to neophobia and enhanced neophobia were produced by consistent differences in drinking rates which appeared early in the 10-min period. The disappearance of neophobia and enhanced neophobia in a 1-hr single-bottle test suggested that the effects of neophobia and enhanced neophobia are short-lived and are best measured in a brief single-bottle test. Finally, enhanced neophobia was not found when 2 days of water drinking were interposed between LiCl poisoning and saccharin testing.