A perivascular hyaline material (PHyM) was found in gingival biopsies from patients with periodontitis, gingivitis and minimally inflamed gingiva. PHyM was found only in association with the sulcular or pocket epithelium. The extent and frequency of the deposits was quantitatively associated with inflammation of the gingival tissues, as well as with the apical region of periodontal pockets. Evidence for angiogenesis was found in association with the deposition of PHyM. The ultrastructure of the PHyM indicated that the material, which was of an amorphous hyaline appearance at the light microscope level, was composed of multiple basal lamina impregnated with irregular collagen fibrils, fine fibrils and cellular debris. The basal lamina material was degraded at many sites. Immunohistochemistry confirmed the abundance of type IV collagen, supporting the basal lamina origin for PHyM. It is proposed that the deposition of the hyaline matrix is related to the effect of angiogenic and injurious agents on the vascular endothelium. PHyM could contribute to the development of periodontitis by impairing the emigration of polymorphonuclear leukocytes into the gingival sulcus.