From an otological standpoint, Lyme disease can manifest itself as Ménière's disease both clinically and electrophysiologically. The aim of this study was to describe the findings of routine clinical, auditory and vestibular tests in patients with Ménière's and Lyme disease and to use electrocochleography (ECoG) to assess the presence of endolymphatic hydrops (EH) in both diseases. Transtympanic ECoG was performed in 91 patients with Ménière's disease and in 11 patients with confirmed Lyme disease. In both diseases the majority of patients had more than one complaint. There was one case with isolated hearing loss in the Lyme disease group. Typical clinical manifestations of Ménière's disease (vertigo, sensorineural hearing loss and tinnitus) were found in 6/11 patients (54.5%) in the Lyme disease group. The ECoG results indicated that there were 65/91 patients (71.4%) with Ménière's disease and 5 patients (45.5%) with Lyme disease who presented with EH. No statistically significant difference was found between the incidence of different symptoms of Ménière's and Lyme disease. On the basis of these results, patients with Lyme disease should undergo careful examination and investigation, especially in endemic regions. The presence of EH does not exclude the presence of infection with borreliosis as a cause of Ménière's disease-like symptoms.