• The characteristic conjunctival scarring in cicatricial pemphigoid is a consequence of subepithelial fibrosis. The fibroblast is the cellular element responsible for fibrosis. To increase the understanding of the pathogenesis of abnormal fibrosis in cicatricial pemphigoid, the growth characteristics of conjunctival fibroblasts, from untreated patients with cicatricial pemphigoid (n = 9) and normal controls (n = 6), were studied in tissue culture. The latent period until fibroblast outgrowth began from the conjunctival explant was determined, as were the plating efficiency and doubling time of cells from first-passage cultures. Outgrowths of fibroblasts from patients with cicatricial pemphigoid appeared significantly sooner than from controls, 8.1 3.8 vs 19.3 ± 6.4 (mean ± SD) days. While there was no significant difference in the plating efficiency between fibroblasts from cicatricial pemphigoid (mean ± SD, 116.4% ± 44.6%) and those from controls (71.0% ± 39.4%), the doubling time was significantly faster for cicatricial pemphigoid than for controls, 26.5 ± 8.5 vs 50.7 ± 7.8 hours. Thus, conjunctival fibroblasts from patients with cicatricial pemphigoid are hyperproliferative in tissue culture when compared with normal controls. Therefore, scarring, which characterizes cicatricial pemphigoid, may be due, in part, to excessive fibroblast proliferation.