Ten patients with amyotrophic lateral sclerosis (ALS) were evaluated through psychiatric interviews and psychological tests. A pattern of active mastery and habitual exclusion of affect from awareness emerged from the premorbid histories of these patients. Reactions to ALS included continued attempts at mastery and persistent suppression, denial, and isolation of depressive and anxious feelings. Psychological tests confirmed the findings of a characteristic style of active mastery and suggested current denial of affect. These observations suggest that an individual's response to an incapacitating illness reflects and perhaps can be predicted from his premorbid life style. The role of unresolved, covert depression on the course of ALS remains to be demonstrated. The association of ALS with a characteristic personality style, if confirmed, might have etiologic and prognostic implications.