Trabeculectomy is a commonly performed procedure for primary open angle glaucoma and is successful in the majority of cases. However, certain factors including aphakia, previous surgery, secondary glaucomas, ethnic origin, and the long term use of topical antiglaucoma medications may be associated with a reduced success rate. The mechanism (or mechanisms) which influence clinical outcome following trabeculectomy remain elusive. Alterations in the composition of the conjunctiva or aqueous humour may be partly responsible for this effect, and this could be mediated by cytokines. In this study we found that tumour necrosis factor (TNF), and interleukin 1 (IL-1) were capable of stimulating the proliferation of Tenon's capsule fibroblasts in tissue culture. Interleukin 6 (IL-6) did not appear to have any effect. The relevance of this to wound healing following trabeculectomy is discussed.