Background Adequate recognition of mental health problems is a prerequisite for successful treatment. Although most people tend to consult their general practitioner (GP) when they first experience mental health problems, GPs are not very well equipped to screen for various forms of psychopathology to help them determine clients’ need for treatment. Objective In this paper, the development and characteristics of CATja, a computerized adaptive test battery built to facilitate triage in primary care settings, are described, and first results of its implementation are reported. Methods CATja was developed in close collaboration with GPs and mental health assistants (MHAs). During implementation, MHAs were requested to appraise clients’ rankings (N=91) on the domains to be tested and to indicate the treatment level they deemed most appropriate for clients before test administration. We compared the agreement between domain score appraisals and domain score computed by CATja and the agreement between initial (before test administration) treatment level advice and final treatment level advice. Results Agreements (Cohen kappas) between MHAs’ appraisals of clients’ scores and clients’ scores computed by CATja were mostly between .40 and .50 (Cohen kappas=.10-.20), and the agreement between “initial” treatment levels and the final treatment level advised was .65 (Cohen kappa=.55). Conclusions Using CATja, caregivers can efficiently generate summaries of their clients’ mental well-being on which decisions about treatment type and care level may be based. Further validation research is needed.