The proposed project goal is to determine which validated bipolar disorder instrument is most acceptable and helpful to patients and clinicians in clinical care, demonstrate that the preferred instrument can be used to monitor outcomes with high fidelity in routine care, and assess the feasibility of comparing effectiveness of measurement-based care (MBC) to usual care in a randomized trial. Many individuals with bipolar disorder experience fluctuating depressive and manic symptoms which can impair functioning and reduce quality of life. Measurement based care (MBC) is an emerging best practice involving serial assessment of clinical status and using those findings to inform clinical decision making. When implemented with fidelity, MBC helps clinicians adjust treatment to “treat to target”. However, no studies have determined preferred bipolar disorder measures for use in clinical care. Furthermore, adoption of MBC for individuals with bipolar disorder has had especially low uptake in routine care. The lack of consensus about which measure to use in serial assessment of bipolar disorder clinical status is likely due to the difficulty of assessing clinical status for patients with bipolar disorder. There are multiple ways to measure clinical status including measuring functioning or symptoms, and when measuring symptoms, there is a need to measure changes in both depressive and manic symptoms. Specifically, there may be uncertainty about how to interpret symptom scale results with respect to weighing the importance of depression and manic symptom severity (particularly when they vary in opposite directions between time points). There is a need to determine the optimal measure for use in MBC for individuals with bipolar disorder. Aims of this R34 include: 1) Using qualitative methods, obtain input from people with bipolar disorder to choose the preferred instrument for monitoring bipolar disorder clinical status that is acceptable, helpful, and understandable in informing when to change treatment. In Aim 1 we expect to identify an Identify an MBC instrument that is perceived to be acceptable, helpful, and understandable to patients diagnosed with bipolar disorder. Next, in Aim 2) In a single arm open trial, assess the feasibility of MBC with the preferred instrument for bipolar disorder and assess fidelity to the protocol including instrument administration, scoring, and reviewing results. In Aim 2 we expect to achieve high fidelity to the MBC protocol. In Aim 3) Conduct a randomized pragmatic pilot effectiveness trial comparing the MBC with the preferred instrument for bipolar disorder to usual care. We will test the Aim 3 hypothesis that treatment adjustments will occur more often in the MBC group than the usual care group, and the exploratory hypothesis that symptoms of bipolar disorder will decrease more in the MBC group than the usual care group. These findings will support an R01 application to conduct a definitive randomized trial.