Registration of observational studies does not enhance validity.

Mandatory registration of observational studies has been proposed to enhance quality of published research and reduce selective publication of positive findings. Enhanced communication of study plans would be welcome, but the alleged benefits to research quality are illusory. In particular, prespecification of hypotheses has no independent effect on data quality or the likelihood that hypotheses are correct. Registration of studies and hypotheses is likely to be misinterpreted as an independent determinant of validity.