Recently, several RCTs have provided preliminary evidence that cognitive-behavioural therapy (CBT) is effective in the treatment of people suffering from schizophrenia. However, none of these trials has provided complete demonstrations of therapist adherence. Since no suitable scale existed already, the authors devised the Cognitive Therapy for Psychosis Adherence Scale (CTPAS). The main aim of the present research was to test whether the 12 items of this scale could be rated reliably. Ratings were made on 29 sessions of CBT for schizophrenia by two raters independently and their agreement was found to be at least adequate on 10 of the items of the CTPAS. Ratings were also made on relevant items of the Collaborative Study Psychotherapy Rating Scale and agreement was found to be more than adequate for three factor-based subscales derived from these items. The results suggest therapist adherence to CBT for psychosis can be rated reliably and that the CTPAS is likely to be useful in future research on this form of treatment.