125 male subjects belonging to infertile couples with negative or doubtful PCT underwent the following tests: IgG MAR Test, seminal TAT, indirect IgG-IgA-IgM-IBT in the seminal plasma, serum TAT, serum SIT, serum IgG-IgA-IgM-IBT. There was no significant difference in the incidence of autoimmunized patients and those resulting from classical testing methods (IgG MAR Test, seminal and serum TAT, serum SIT) (16%), and the results of the indirect IBT in the seminal plasma and in the serum (16.8%). The IBT showed an increase which was not, however, statistically significant in subjects with concomitant local and general autoimmunization, compared to the classical methods, (13.6% in the subjects examined versus 10.4%). There was a statistical significant difference between the results of the indirect IgA-IBT in the seminal plasma and those of the IgG MAR Test, (19 versus 12 positive patients, chi2 = 6.05, p less than 0.05). Furthermore, in 88.2% of the cases with concomitant positivity, the indirect IgA-IBT in the seminal plasma showed higher values than the indirect IgG-IBT in the seminal plasma. There was no significant difference between the results of the classical methods and the serum IBT, whereas both in the semen and in the serum the beads adhered mainly to the tail plus the tail up considering only the nemaspermic portion with the highest relative rate of adhered beads.(ABSTRACT TRUNCATED AT 250 WORDS)