Aim of Work: The aim of our work was early cytological and laboratory detection of any ocular surface malignant changes in xeroderma pigmentosa. Patients and Methods: Eighteen cases with xeroderma pigmentosa were included in this study. All cases were subjected to full ophthalmolog-ical examination, conjunctival biopsy from any abnormal lesion, polymerase chain reaction assay and impression cytology. Results: All cases were boys;the mean age was 11 years old. The main ocular presentation was dryness and abnormal epibulbar masses in different locations. Polymerase chain reaction represents precipitation of malignant cells which was confirmed by impression cytology. Conclusion: PCR and impression cytology are beneficial investigations for detection of any malignant changes in xeroderma pigmentosa.