The Ouchterlony - Elek gel diffusion test was performed in twenty-nine patients having a positive culture result for diphtheria bacilli on Loeffler and tellurite agars in January and February, 1984 and toxin production was detected in 20 of them. Except one adult patient, the cases ranged in age 2 and 12 years. In 14 patients who have received at least one immunization with diphtheria vaccine had no complication, besides three patients without immunization in whom two received antibiotics plus antitoxin therapy had carditis and soft palate paralysis. Five patients in the non-immunized group and 6 patients in the group received at least one immunization had diphtheritic membrane. In spite of three patients with cardiac and neural complications, with early diagnosis and beginning therapy with antibiotics and antitoxin before the result of in vitro toxigenicity test, O% mortality rate was obtained.