Five studies tested the hypotheses that there are individual differences in the frequency of automatic thoughts involving perfectionism and that these thoughts are associated with psychological distress. Research with the Perfectionism Cognitions Inventory (PCI) established that this new measure has adequate psychometric properties, and high PCI scorers tend to spontaneously report perfectionistic thoughts in naturalistic situations. Additional research confirmed that frequent perfectionism thoughts account for unique variance in distress, over and above variance predicted by standard measures of negative automatic thoughts and trait perfectionism measures. Overall, the findings support the view that personality traits involved in depression and anxiety have a cognitive component involving ruminative thoughts and that activation of this cognitive personality component contributes to distress.