On the basis of elevated levels of seminal plasma immunoglobulins and a decreased production of LMI in the presence of PPD, 6 patients (out of the idiopathic normogonadotrophic oligospermic group) were selected for a therapeutic trial with levamisole. The following regime of treatment was applied: 3 days on levamisole (150 mg per day) followed by a 10 day interval without treatment, for a period of three months. The sperm count increased in 5 out of 6 patients and motility increased in 2. At the same time a reduction in seminal plasma IgG levels was observed in all treated patients. A significant increase of EA rosettes was observed after treatment.