Monoclonal antibodies were used to assess the lymphocyte populations in conjunctival biopsy specimens obtained from patients with trachoma (active or inactive) undergoing tarsotomy for the correction of trachoma-induced entropion and in three control patients. Peroxidase-labelled monoclonal antibodies OKT4 (identifies T-helper/inducer lymphocytes), OKT8 (identifies T-suppressor/cytotoxic lymphocytes), OKIal (identifies B-lymphocytes) and antisera specific for IgG, IgA and IgM were used to identify lymphocyte subpopulations and immunoglobulins in the conjunctival biopsy specimens. When grouped by disease activity, conjunctival tissue specimens revealed predominant T-helper/inducer lymphocytes in the substantia propria of patients with active trachoma while inactive trachoma patients had predominant T-suppressor/cytotoxic lymphocytes in the conjunctival biopsy specimens. B-lymphocytes were seen in moderate numbers in all conjunctival biopsy specimens from patients with active trachoma and all specimens from active cases stained for IgG, IgM, and IgA. Immunoglobulin staining was strongest with IgG and IgM.