Nitric acid and hydrochloric acid vapors may condense in the winter polar stratospheres. Nitric acid clouds, unlike water ice clouds, would form at the temperatures at which polar stratospheric clouds (PSCs) are observed and would have optical depths of the magnitude observed suggesting that HNO3is a dominant component of PSCs. ClO, N2O5and ClNO3may react on cloud particle surfaces yielding additional HNO3, HCl, and HOCL. In the vicinity of PSCs these reactions could deplete the stratosphere of photochemically active NOxspecies. The sedimentation of PSCs may remove these materials from the stratosphere. The loss of vapor phase NOxmight allow halogen‐based chemistry to create the ozone hol