equity, and/or value of mental health services. This NOFO is intended to support trials that: address a significant problem, such that the findings have potential to inform practice; are adequately powered to definitively answer the primary research question(s), with well-justified hypotheses supported by pilot data; and are designed to examine questions regarding mediators and moderators of effects. Consistent with the NIMH experimental therapeutics approach, this NOFO is intended to support effectiveness trials that explicitly address whether the intervention engages the target(s)/mechanism(s) presumed to underlie the intervention effects (i.e., the mechanism(s) that accounts for changes in clinical/functional outcomes, changes in provider behavior, improved access or continuity of services, etc.). The collaborative R01 mechanism provides support for multisite trials when two or more sites are necessary for completion of the trial (e.g., to increase sample size, accelerate recruitment, or increase sample diversity and representation).