Objective: Oral pulse granuloma (OPG) is an oral inflammatory lesion characterized by the presence of hyaline rings with numerous multinucleated giant cells. The etiopathogenesis of this lesion is thus far unclear, as is the composition of the hyaline rings. Our aim was to investigate whether the hyaline rings contain cellulose. Study Design: Using a newly developed staining method for cellulose, we studied 18 histologic samples diagnosed as OPG, in addition to 3 samples originally diagnosed as "normal" foreign body reactions. In our study, visualization of cellulose is based on its specific binding to the carbohydrate binding module of β-1,4-glycanase. Results: All samples diagnosed as OPG were positive for cellulose staining localized in hyaline rings. In addition, 1 lesion (of 3), first diagnosed as a foreign body reaction without the presence of hyaline rings, was positive for cellulose by horseradish peroxidase staining. Conclusions: We show for the first time that cellulose is present in OPG lesions, indicating that cellulose might be the initial cause of formation of these lesions.