Two measures assessed 4-10-year-olds' and adults' (N = 201) understanding of future likelihood and uncertainty. In one task, participants sequenced sets of event pictures varying by one physical dimension according to increasing future likelihood. In a separate task, participants rated characters' thoughts about the likelihood of future events, their emotions, and their decisions in indeterminate social situations. Results showed significant development between ages 4 and 10 in seriating events according to future likelihood and in selecting thought and emotion ratings indicative of future uncertainty. Higher performance on the future likelihood ordering task correlated with greater understanding of future uncertainty in thought, emotion, and decision judgments. Females judged future events to be more uncertain than males. (Contains 5 tables and 3 figures.)