A “successful” medical research grant proposal can be defined in two ways: (1) one to which reviewers assign a high enough priority score to attract funding to do the project, (2) one that results in study conclusions that benefit clinical decision making for the population sampled and/or moves research in that field a little forward. This discussion focuses on the issue of assessment and its effect on the success of a proposal. The quality of data (reliability, validity, sensitivity, level) is briefly reviewed. Questions are addressed related to how much data is too little, and how much data is too much, which data are necessary and/or desirable, and which might actually undermine the goals of the study, concluding with a few comments on issues related to data acquisition, cleaning, storing, monitoring and access. The connection between the data one intends to collect and the wisdom one hopes to gain from that data is fragile. Thus it is essential to structure proposals that will pass muster with review committees and that will contribute both to clinical decision making and scientific progress.