A controlled study of the ciliated epithelium of olfactory mucosa was performed on 25 patients affected by retinitis pigmentosa and in 5 healthy subjects. Scanning Electron Microscopy showed a significant lack of ciliated epithelial cells. These cells probably represent undifferentiated ciliated cells. These morphological alterations of the olfactory mucosa might correspond to similar changes in the outer segment of retinal photoreceptors in retinitis pigmentosa.