Although tests of young children's understanding of mind have had a remarkable impact upon developmental and clinical psychological research over the past 20 years, very little is known about their reliability. Indeed, the only existing study of test–retest reliability suggests unacceptably poor results for first-order false-belief tasks (Mayes, Klin, Tercyak, Cicchetti, & Cohen, 1996), although this may in part reflect the nonstandard (video-based) procedures adopted by these authors. The present study had four major aims. The first was to re-examine the reliability of false-belief tasks, using more standard (puppet and storybook) procedures. The second was to assess whether the test–retest reliability of false-belief task performance is equivalent for children of contrasting ability levels. The third aim was to explore whether adopting an aggregate approach improves the reliability with which children's early mental-state awareness can be measured. The fourth aim was to examine for the first time the test–retest reliability of children's performances on more advanced theory- of-mind tasks. Our results suggest that most standard and advanced false-belief tasks do in fact show good test–retest reliability and internal consistency, with very strong test–retest correlations between aggregate scores for children of all levels of ability.