A computerized adaptive Finnish speech-in-noise test has recently been developed. The purpose of the present study was to measure speech recognition thresholds in noise (SRTN) in patients with sensorineural hearing impairment (SNHI) caused by mitochondrial mutation [mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS)] and in patients with SNHI from other causes and to compare them with those in normal hearing controls. SRTN differed significantly between controls and the patients with SNHI from other causes and between controls and the MELAS group, but not between SNHI patients and the MELAS group. Hearing in a noisy environment seems to be as impaired in MELAS patients as in patients with SNHI from other causes, in spite of the possible coexisting defects in the central nervous system.