To determine the correlation between the lymphocyte transformation test (LTT) with phytohemagglutinin (PHA) and the clinical forms of American leishmaniasis (AL), duration of the disease and reaction to leishmanin, the authors studied 12 patients and compared them to 25 unaffected individuals. The ulcerated cutaneous form of the disease was observed in 4 patients, the ulcero-nodular lymphangitic form in 1 the mucous cutaneous form with destruction of the nose in 6, and the verrucous form in 1. General patient condition was satisfactory and the Montenegro reaction macroscopically positive with infiltrations of 5–15 mm in diameter. The results revealed no evidence of immunodeficiency among patients. No correlation was observed between clinical forms, duration of the disease and Montenegro reaction and LTT results. LTT with PHA does not appear to be an adequate indicator of the cell immune system in AL case