Children often perseverate, repeating prior behaviors when inappropriate. This work tested the roles of verbal labels and stimulus novelty in such perseveration. Three-year-old children sorted cards by one rule and were then instructed to switch to a second rule. In a basic condition, cards had familiar shapes and colors and both rules were stated explicitly. In an uninformative-label condition, cards had familiar shapes and colors, but the first rule was not stated explicitly. In a novel-stimuli condition, both rules were stated explicitly but stimuli were novel on the first sorting dimension. More children switched to the second rule in the uninformative-label and novel-stimuli conditions than in the basic condition. Implications for theories of cognitive flexibility are discussed.