Background: Studies of cognitive behavioural therapy (CBT) for psychosis 'a debilitating illness of the mind, often characterised by symptoms such as hallucinations, delusional beliefs, thought disorder and bizarre behaviours' demonstrate that African Caribbean and Black African patients have higher drop-out rates and poor outcomes from treatment. Aims: a). To produce a culturally sensitive adaption of an existing CBT manual for therapists working with patients with psychosis from African-Caribbean, Black- African/Black British, and South Asian Muslim communities. b). To assess the effectiveness of culturally adapted CBT for psychosis in this population. Method: Part 1: A two centre qualitative study consisting of individual semi-structured interviews with patients with a diagnosis of schizophrenia, schizo-affective, delusional disorders or psychosis (n=15); focus groups with lay members (n=52); CBT therapists (n=22) and mental health practitioners (n=25). Data was analysed thematically using evolving themes and content analysis. NVivo 8 was used to manage and explore data. Part 2: The recommendations were used to inform adaptation of CBTp. A randomised controlled trial was conducted in three centres in the UK. A total of 35 participants were recruited. Assessors blind to randomisation and treatment allocation administered outcome measures at three-time points; baseline, post-therapy and at 6 months follow-up using the Comprehensive Psychopathological Rating Scale (CPRS) and Insight in Psychosis Scale. Participants in the CaCBTp arm (n=16) were offered 16 sessions of therapy and completed Patient Experience Questionnaire (PEQ) post-treatment. Treatment as usual (TAU: n=17) arm continued with standard their treatment. Results: Analysis was based on the principles of intention to treat (ITT). This was further supplemented with secondary sensitivity analysis. Post-treatment the intervention group showed statistically significant reductions in symptomatology on overall CPRS scores, CaCBTp group, Mean (SD) = 16.23 (10.77), TAU = 18.60(14.84); p = 0.047, with a difference in change of 11.31 (95% CI: 0.14 to 22.49; CPRS subscales showed significant effect in CaCBTp over TAU. Adjustment was made for age, gender and medication. Overall satisfaction on the PEQ was significantly correlated with the number of sessions attended (r= .563; p = 0.003). Conclusion: Participants in the CaCBTp group achieved statistically significant improvement post-treatment compared to the TAU. Attrition rates were low and therapy experience and satisfaction were highly rated. The findings will have implications for a definitively powered phase III RCT. A CaCBTp training manual in is preparation.