  We critically examine the validity of the Weizs\"acker-Williams approximation
in electron-hadron collisions. We show that in its commonly used form it can
lead to large errors, and we show how to improve it in order to get accurate
results. In particular, we present an improved form that is valid beyond the
leading logarithmic approximation in the case when a small-angle cut is applied
to the scattered electron. Furthermore we include comparisons of the
approximate expressions with the exact electroproduction calculation in the
case of heavy-quark production.
