Tumor biomarker studies may generate insights into the biological characteristics that drive the clinical behavior of a cancer. Publication bias and hidden multiple hypotheses testing distort the assessment of the true value of biomarkers. Publication bias from preferential reporting of 'positive' findings is well recognized. Hidden multihypothesis testing arises from several biomarkers being tested by different teams using the same samples. The more hypotheses (that is, biomarker association with outcome) tested, the greater the risk of false-positive findings. These biases inflate the potential clinical validity and utility of published biomarkers while negative results often remain hidden. Trial registries have been developed where all phase II and phase III trials should be listed regardless of study outcome. However, such steps have not been taken to reduce such bias in tumor biomarker research. We propose that a registry should be created for biomarker studies initially focused on studies that use specimens from randomized trials. Further development could include nonrandomized studies and deposition of raw data similar to existing genomic data repositories. The benefits of a comprehensive biomarker study registry include more balanced evaluation of proposed markers, fewer false positive leads in research, and hopefully more rapid identification of promising candidate biomarkers.