Primary hyperhidrosis is a dermatological condition involving excessive sweating. Stress and emotional cues play a significant role in the onset of sweating, but little research has been conducted on this aspect of the condition. A cognitive-behavioral approach to hyperhidrosis would suggest that dysfunctional beliefs about the nature and consequences of sweating play a role in increased sweating. I investigated the psychometric properties and construct validity of a new measure of the cognitions hypothesized to be involved in hyperhidrosis: the Sweating Cognitions Inventory (SCI). The SCI demonstrated good internal consistency and a stable, unidimensional factor structure in both a clinical sample of individuals diagnosed with hyperhidrosis and a student comparison group. Sweating cognitions differentiated between the two groups, indicating discriminative validity. Correlations indicated that sweating cognitions were strongly related to sweating severity, and also social anxiety and anxiety sensitivity. Implications for the conceptualization and treatment of hyperhidrosis are discussed.