Background: Routine Outcome Monitoring (ROM) has become part of the treatment process in mental health care. However, studies have indicated that few clinicians in psychiatry use the outcome of ROM in their daily work. The aim of this study was to explore the degree of ROM use in clinical practice as well as the explanatory factors of this use. Methods: In the Northern Netherlands, a ROM-protocol (ROM-Phamous) for patients with a psychotic disorder has been implemented. To establish the degree of ROM-Phamous use in clinical practice, the ROM results of patients (n = 204) were compared to the treatment goals formulated in their treatment plans. To investigate factors that might influence ROM use, clinicians (n = 32) were asked to fill out a questionnaire about ROM-Phamous. Results: Care domains that were problematic according to the ROM-Phamous results were mentioned in the treatment plan in 28% of cases on average (range 5-45%). The use of ROM-Phamous in the treatment process varies considerably among clinicians. Most of the clinicians find ROM-Phamous both useful and important for good clinical practice. In contrast, the perceived ease-of-use is low and most clinicians report insufficient time to use ROM-Phamous. Conclusions: More frequent ROM use should be facilitated in clinicians. This could be achieved by improving the fit with clinical routines and the ease-of-use of ROM systems. It is important for all stakeholders to invest in integrating ROM in clinical practice. Eventually, this might improve the diagnostics and treatment of patients in mental health care. (C) 2016 Elsevier Masson SAS. All rights reserved.