Eight specimens each of the following groups were investigated: gingival pyogenic granuloma, fibrous epulis, calcifying fibrous epulis, peripheral giant cell granuloma, giant cell fibroma (four gingival, four non-gingival), denture-irritation hyperplasia and fibroepithelial polyp. These lesions have diverse histopathological appearances but the composition of their connective tissue is poorly defined. The elastic system consists of a complex mixture of glycoproteins that in normal oral mucosa form three differentially distributed fibre types; oxytalan, elaunin and elastic. The elastic system was investigated by Verhoeff's haematoxylin stain, aldehyde fuchsin staining and an anti-elastin monoclonal antibody. Elastin was identified in all fibroepithelial polyps and denture-irritation hyperplasias, but in none of the other lesions. In particular, this identified a distinct difference in the extracellular matrix between the giant cell fibroma and fibroepithelial polyp. Many of the epulides included only oxytalan fibres, but the presence of oxytalan fibres did not follow any pattern within either a single lesion group, or between different lesions. However, the presence of oxytalan fibres in the absence of elastin does not necessarily support a periodontal ligament origin for reactive epulides.