It is known that secondary endolymphatic hydrops occurs in patients with unilateral and/or bilateral profound hearing loss. Schuknecht summarized this disease as 'delayed endolymphatic hydrops (DEH)'. This report includes 35 patients with DEH, 17 of whom were diagnosed as suffering from the ipsilateral type and 18 from the the contralateral. Transtympanic electrocochleography (ECochG) was performed on the better-hearing ears of these patients. The results showed an increased negative summating potential to 100dB click stimulus in 11 out of 16 contralateral DEH patients, whereas it could be measured in none of 10 ipsilateral DEH patients. The mean SP/AP ratio for the contralateral type was 0.46, which was significantly larger than that for the ipsilateral type. The results suggest taht contralateral-type DEH has the same pathology in the cochlea as Meniere's disease, and that performing ECochG on the better hearing ear is indispensable in distinguishing the two types of DEH.