Some immunological parameters in three white patients who contracted loaiasis in endemic areas are reported. Microfilariae count in peripheral blood was elevated in one patient, discrete in another while in the third no microfilariae were detected. Serum IgE levels were elevated in two patients and normal in one of them. High eosinophils percentage (greater than 30%) and high titres of specific anti-filarial antibodies were detected in all patients. C3 and C4 levels fell between the normal values and C3PA was low in one patient. No circulating immune complexes were demonstrated. Two patients showed high anticomplementary activity. Our results are in accord with the possibility of a suppression mechanism in immune response in patients with high microfilaremia. Clinical features of loaiasis could be related to a type 1 (reaginic) reaction.