As our knowledge of the histopathology of common colds is very limited, we have undertaken a blind quantitative examination by scanning electron microscopy and light microscopy of 56 nasal biopsies, taken from 29 volunteers with naturally acquired colds. In agreement with earlier reports we found evidence of sloughing of epithelial cells, but in contrast to in vitro experiments, this did not result in a destruction of the epithelial lining, which by and large remained continuous, with structurally normal cell borders. There was a significant increase in the number of neutrophils, both in epithelium and in lamina propria, already on the 2nd day of the disease, and the hypothesis is advanced that the virus infection itself is the cause of the local neutrophilia. The only other abnormality demonstrated was an increased number of extracellular erythrocytes in the acute stage. The histological picture was not suggestive of an involvement of epithelial mast cells in the inflammation.