  In this talk I review measurements and calculations of the flux of neutrinos
produced by interactions of cosmic rays in the atmosphere. The main reason for
interest in this subject is the apparent anomaly between the predicted and the
observed ratio of $\nu_e$ to $\nu_\mu$. With the advent of Super-Kamiokande, we
are on the threshold of an order of magnitude increase in the amount of data
available to study the problem. My goal in this talk is to describe the current
status of the subject, both for contained events and for neutrino-induced
upward muons.
