Résumé : Abstract—Antisera that recognize specifically UV‐photoproducts in DNA have been used to follow the elimination of photolesions in UV irradiated Tetrahymena pyriformis. The amount of bound tritiumlabelled antibodies to nuclei has been estimated by autoradiography. Curves of dose‐response of DNA photoproducts, their elimination by dark repair, and effect of caffeine, quinacrine and chloroquine on the disappearance of UV‐lesions have been evaluated. Copyright © 1979, Wiley Blackwell. All rights reserved