A pseudocaloric nystagmus is, in its strict sense, a spontaneous nystagmus activated by the unspecific stimulus of syringing the auditory canal. 40 patients with a unilateral, peripheral-vestibular defect were examined electronystagmographically. With most patients the 30 degrees caloric stimulation gave an incorrect result of the degree of hypoexcitability with all parameters (duration, maximum frequency and maximum intensity). This incorrect result was most pronounced with patients after neurectomy of the vestibular nerve, who frequently had a heavily reduced reaction of the healthy ear. For quantitative measurement of genuine pseudocaloric effects, by a special method of examination (as for instance by consideration of the "maximum spontaneous nystagmus"), the "real" vestibular excitability was calculated. Data exceeding this value were regarded as genuine pseudocaloric nystagmus. At stimulation temperatures of 44 degrees to 17 degrees C they were so low as to be negligible. They were only found with 5 of the 40 patients and amounted to only 10-20% of the reaction of the healthy ear. However, with ice water there frequently were considerable pseudocaloric reactions. So testing with ice water is not appropriate.