Relations among effortful control/low negative emotionality, immediate reactions in a situation that usually calls for the masking of disappointment (i.e., the use of display rules), and social competence/adjustment were investigated for 78 preschool children (mean age=4.87 years). Parents, teachers, and peers rated children on negative emotionality and/or effortful control as well as on social competence/adjustment. Children who were rated by parents and teachers as high on effortful control/low on negative emotionality expressed fewer immediate verbal/gestural indicators of disappointment in the presence of an unfamiliar adult and were perceived by their parents, teachers, and peers as socially competent and well adjusted. The pattern of findings was consistent with the view that children's immediate verbal/gestural reactions to disappointment partially mediated the relations between effortful control (as reported by parents) and social competence/adjustment.