We conducted a histopathologic study of he meibomian glands of seven patients (all men, ranging in age from 58 to 83 years) who had severe or moderately severe meibomian dysfunction and who were undergoing ectropion or entropion repair. Abnormal features included signs of obstruction and dilatation of ducts, enlargement of acini with cystic degeneration and squamous metaplasia, foreign-body reaction and granuloma formation, a mild increase in inflammatory cells, and abnormal keratinization. Demodex organisms were found in both acini and ducts of one patient. These findings were similar to those reported in other entities involving meibomian duct obstruction, probably related to abnormalities of keratinization, plays an important role in the pathogenesis of meibomian gland dysfunction.