We studied 44 patients who had dacryocystorhinostomy for primary acquired complete nasolacrimal duct obstruction. The lacrimal sac and nasal mucosa adjacent to the osteotomy were examined histologically. The lacrimal sac had chronic inflammatory changes in 33 of 37 patients with varying degrees of fibrosis in 34 of 37. Focal ulceration of the lacrimal sac epithelium was present in 15 cases. Goblet cells, present in 11 specimens, were not identified in 26 specimens. Moderate or severe chronic inflammation was found in 14 of 44 nasal mucosal specimens and marked fibrosis in 22. The pathology of the lacrimal sac and nasal mucosa is similar to that of the nasolacrimal duct in complete nasolacrimal duct obstruction. The nasal inflammation may have resulted from dacryocystitis or alternatively contributed to the dacryocystitis.