Non-adherence to treatment of patients with psychotic disorders is related to higher rates of relapse, hospitalization, and suicide. Important predictors of non-adherence include poor social structure, cognitive deficits, negative medication attitude, side effects, depression, a sealing-over recovery style, feelings of stigmatization, denial of treatment need, and lack of insight. Attempts to improve adherence have shown that psychoeducation alone is not fully effective, and that motivational interviewing, behavioral strategies, and linking a patient s personal goals to treatment may increase adherence. Based on the empirical data reviewed, we formed four clusters of possible causes of non-adherence, each of which can be targeted by a specific module of our developed Treatment Adherence Therapy (TAT). These four modules are: self-enhancement, motivational interviewing, medication dosage trials, and behavioral training. An individual patient may benefit from one or more of these modules; and thus the contents of TAT vary in accordance with individual causes of non-adherence. Basically, TAT aims to help patients work out what they want regarding treatment and then support them in following this through. TAT will be investigated in a multicenter randomized clinical trial in the Netherlands, starting March 2006.