In this thesis, chapter 2 presents the protocol of the SUPRANET Care implementation study. The SUPRANET Care study (N=13) uses an uncontrolled longitudinal prospective design, collecting data on on the following three study outcomes by using a 2-level structure (institutional level and team level): 1] reduced suicide rates, 2] improved registration of suicide attempts, and 3] improved professionals’ knowledge and adherence towards the suicide prevention guideline. In chapter 3, a Delphi study is described. An expert panel of 90 participants scored 11 quality indicators (QIs) on two criteria (relevance and action orientation). Data analysts (n=6) from the participating institutions rated the QIs on a third criterion: feasibility. We found that 5 QIs were scored as relevant and action oriented: 1] screening for suicidal thoughts and suicidal behavior, 2] safety plans, 3] early follow-up on discharge, 4] continuity of care, and 5] family- or caretaker involvement. Only one indicator reached consensus on feasibility: early follow-up on discharge. In chapter 4 of this thesis, a total of 400 mental health care professionals were included, working in 22 teams (crisis teams and ambulatory care teams) across 12 institutions. Although the majority of mental health professionals (N=400) scored relatively high on professionals’ knowledge, and attitude during baseline, most of them were not aware to what extent the guideline was used by their colleagues (i.e. adherence towards the guideline). After the data was analyzed on team level, we found that crisis teams scored significantly better on professionals’ knowledge (B(95%-CI)=2.00(1.32-2,67); p