Children's reasoning about the stability of human psychological characteristics was investigated in relation to the obligatory distinction between the Spanish verb forms ser and estar (which convey different information about the stability of characteristics) and the corresponding English form to be. Participants (85 bilingual children, ages 6 to 10 years) were interviewed to determine (a) whether the ser/estar distinction is relevant to reasoning about the stability of human characteristics and (b) whether beliefs about the stability of psychological characteristics relate to differences in the use of ser and estar to describe and explain social events. Children treated ser and to be as more likely than estar to convey the stability of psychological characteristics. Children who tended to endorse stable views of psychological characteristics were especially likely to use the ser form in their descriptions and explanations.