Gingival biopsy specimens from eight patients exhibiting a localized, erythematous, or mixed erythematous/leukoplakic gingivitis that was refractory to conventional periodontal therapy were examined histologically and by energy-dispersive X-ray microanalysis. Histologic examination revealed variable numbers of small, usually subtle, sometimes equivocal, and occasionally obvious foci of granulomatous inflammation. Special stains for fungi and acid-fast bacilli were consistently negative. In all cases, the granulomatous foci contained particles of foreign material that were often inconspicuous and easily overlooked during routine histologic examination. Energy-dispersive X-ray microanalysis of these foreign particles disclosed Ca, Al, Si, Ti, and P in most lesions. However, other elements such as Zr, V, Ag, and Ni were found only in specific biopsy specimens. By comparing the elemental analyses, clinical features, and history of the lesions, strong evidence for an iatrogenic source of the foreign material was found in one case, and good evidence in five cases. In the remaining two patients, the source of the foreign particles remains unresolved.