We investigated the contribution of temperament and external environment to the severity of children who stutter. Sixty-nine children who stutter, ages 2;4 to 5;9 (years; months), with a mean age of 3;7, were assessed for temperament, home environment, and significant life events. Temperament was assessed using the Children's Behavior Questionnaire. Home environment and life events were assessed using the Confusion, Hubbub and Order Scale (CHAOS) scale and the Life Events Checklist. Results indicated mother (parent)-reported stuttering severity and clinician-reported stuttering severity to be correlated with child temperament scores in the domain of Effortful Control. When temperament, home environment, and life events were combined, no statistically predictive outcomes were evident in corresponding severity ratings. The current study suggests the temperament domain of Effortful Control in children who stutter is a significant underlying mechanism influencing stuttering severity. Clinical implications are discussed.