In many non-human species, learning retention decreases temporarily following training. This has led to the suggestion that these lapses reflect a fundamental component of memory formation. If so, transient memory lapses should also be prevalent in humans, and should occur for all types of learning. In line with these predictions, we report two cases of transient memory lapses in humans that occur 1-3 h after training on a perceptual-discrimination task. The results indicate that the occurrence of transient memory lapses extends to perceptual learning, a form of skill learning, and suggest that transient memory lapses may be a common but overlooked facet of memory formation in humans.