Gingival biopsies from areas characterized as clinically normal, mild gingivitis, or periodontitis were examined. Immunoglobulin (IgG, IgA, IgM, IgE and IgD) bearing cells at the sulcular and oral epithelium -lamina propria junctions as well as the central lamina propria areas were quantitated. Normal gingiva (P. I. = 0-0.2) contained few lymphocytes and plasma cells. Biopsies from areas of mild gingivitis (P.I. = 0.2-1) were infiltrated at the sulcular epithelium -lamina propria junction by lymphocytes lacking membraneassociated immunoglohulins (94 %). Few plasma cells were evident. In contrast, tissue associated with periodontitis (P. I. = 4.0-8.0) contained significant numbers of immunoglobulin hearing lymphocytes (78 %, IgG; 9 %, IgM; and 4 % IgA) and plasma cells (67 %, IgG; 24 %, IgM; and 8 % IgA) distributed throughout all three major tissue areas.These findings indicated that the nature of cellular infiltrates differed in mild gingivitis and periodontitis. The presence of predominantly IgG and IgM containing cells in periodontitis had important implications for the contribution of nonspecific effector mechanisms to the destruction of periodontal tissue. infiltrate has not been resolved. Compara-