Evidence-based health care requires that relevant outcomes for patients are included in clinical trials investigating treatment effects, allowing subsequent systematic reviews to summarize all relevant evidence to guide clinical practice. Currently, no gold standard of outcome choice for dermatology trials and reviews exists. We systematically assessed concordance between efficacy outcomes in a random sample of 10 Cochrane Skin systematic reviews and the 220 dermatology trials included. Reviews did not include 742 (68%) of the 1,086 trial outcomes. Of the 60 outcomes the reviews sought, 17 (28%) were not reported in any trial, while 12 were assessed in <50% of trials. For 11 of 23 (48%) primary review outcomes, meta-analysis was impossible, because trial outcomes were absent or unclear. This small overlap of review/trial outcomes could suggest that trials are not measuring the outcomes perceived to be the most important by patients, clinicians, systematic reviewers, and trialists. The lack of standardized outcome measures, poor reporting of outcomes in trials, and low concordance of outcomes between reviews and primary studies could be improved by the development and implementation of Core Outcome Sets. These are an agreed-upon minimum set of key outcomes, for specified conditions, to be reported in all trials.