Recovery and identificationin vitroof lymphocytes from gingival tissue was carried out for 20 patients with chronic marginal gingivitis. A combination of 90 min incubation in a collagenase‐containing medium followed by mechanical disruption through a stainless‐steel grid resulted in a mean yield of 2.42 × 105(S. D. ± 1.26 × 105: n = 16) lymphocytes per 100 mg or tissue. When Ficoll density centrifugation was introduced into the recovery procedure, the mean lymphocyte yield dropped to 2. 15 × 104(S. D. ± 0.99 × 104: n = 4) per 100 mg. Mean viability of recovered lymphocytes was 78% (S. D. ± 5%: n =16) and for Ficoll separation, 77% (S. D. ± 1%: n = 4). In cell suspensions obtained from 12 or the patients, T lymphocytes were identified by rosette formation with sheep erythrocytes, and B cells were quantitated using fluorescent identification of membrane immunoglobulin. Macrophages were identified on the basis of non‐specific esterase characteristics. Tire predominant lymphocytes round were T cells, with a mean proportion of 53.9% (S. D. ± 5.6%); the mean proportion of B cells was 32.7% (S. D. ± 5.4%). Macrophages accounted for a mean of 7.7% (S. D. ± 2.8%) or the recovered lymphoid cells. The lymphocyte‐plasma cell ratio in recovered cell suspensions was 7:1 compared with a ratio of 1.7:1 noted in his