The biological role of T cell receptor (TCR) gamma delta bearing cells is currently not fully understood. Recently, a monoclonal antibody (TCR delta 1) reacting against the whole molecule became available which facilitates the direct analysis of TCR-gamma delta+ cells. We studied 11 children with atopic dermatitis, 20 children with atopic asthma, 18 adults with atopic dermatitis and 38 healthy age matched controls aged 4-51 years. Lymphocytes were isolated from heparinized peripheral blood and the proportion of TCR-gamma delta+ lymphocytes was determined by FACS analysis. Patients with atopic diseases yielded a significantly (P less than 0.01) lower proportion of TCR-gamma delta+ cells compared with normal controls (median 4.8% versus 7.1%). The percentage of TCR-gamma delta+ cells showed an age-dependent decline in both the patient group (r = -0.49, P less than 0.01) and the control group (r = -0.40, P less than 0.01). In addition, the proportion of cells which expressed CD8, TCR-gamma delta or CD4, TCR-gamma delta simultaneously was determined by double labelling immunofluorescence. Whereas CD4+, TCR-gamma delta+ cells could be identified in only a few individuals, CD8+, TCR-gamma delta+ cells were found in nearly all controls (median 2.4%, range 0.0-10.8%); atopic patients displayed significantly (P less than 0.01) lower proportions of CD8+, TCR-gamma delta+ cells.