The correction for Malmquist bias is generally thought to have the form αΔ 2 , where Δ is the rms fractional error for a given distance indicator and α is a numerical coefficient which depends on the galaxy distribution and other aspects of the problem. In fact, this form of the correction is valid only when the objects are selected on the same observable that is used to make the distance measurement. In many applications of the Tully-Fisher relation, the galaxies are selected from B catalogs, but the distances are measured using H, I, or R magnitudes