The authors examined using the antibody against latent membrane protein (LMP-1) a group of 169 patients with Hodgkin's lymphoma (age 2 to 82 years). From the total number of 169 patients 48 (28%) patients were positive when tested with this antibody. In the whole group the following histological types were represented most frequently: type II (nodular sclerosis) 83 (49%) patients, and type III (mixed cellularity) 70 (41%) patients. Type I (lymphocytic predominance) was not represented. In type IV (lymphocyte depletion) there were three cases (1.7%). Type V (lymphocyte rich) was represented by 13 patients (7.6%). The frequency of positive cases was in these histological types as follows: type II 14 cases (17% of 83 cases), type III 28 cases (40% of 70 cases), type IV 2 cases (66% of 3 cases). type V 4 cases (30% of 13 cases). Distribution of positive cases by age: in children under 10 years a positive finding was recorded in 80%. In old people above the age of 80 years there was a 100% positivity (only two patients were examined). The smallest number of positive cases was in the third decade (of 26 patients 4% were positive). LMP-1 positivity was most frequent in male patients--in 37 (of 96 examined patients) and in 11 female patients (of 73 examined) The frequency of LMP-1 in Hodgkin's lymphoma is consistent with similar studies in economically developed countries. A markedly higher incidence of positive cases in the lowest and highest age groups and gender differences are striking and so far there is no unequivocal explanation for them.