Animals learn to prefer the flavors of foods on the basis of the foods’ postingestive nutritional consequences. This has been demonstrated with the conditioned flavor preference paradigm. With this paradigm, one flavor (the CS+) is paired with a nutrient that is orally consumed or is infused via a post-oral (e.g., intragastric) route; another flavor (CS-) is paired with a nonnutritive source. In subsequent two-choice tests, the rats displayed reliable preferences for the CS+ flavor over the CS- flavor. Very strong preferences (>95%) for sour or bitter flavors have been conditioned in nondeprived rats by pairing the CS+ with intragastric infusions of Polycose during 24-h/day training sessions. These conditioned preferences persisted for several weeks when the CS+ flavor was no longer paired with IG nutrient infusions. Thus, with the appropriate training procedures, conditioned flavor preferences can be as robust as conditioned flavor aversions.