Preyer's reflex, the elicitation of startle response to auditory stimuli, has been widely used for the evaluation of hearing in rodents and other animals. Surprisingly, however, the sensitivity and specificity of Preyer's reflex in the assessment of hearing has not been adequately studied. The aim of this study was to investigate the utility of Preyer's reflex in the evaluation of auditory function in mice. Forty-six adult albino mice on an FVB background with variable hearing loss were used for this study. Two different methods for eliciting a Preyer's reflex were tested: a handclap and a sharp metallic sound. The reflex was considered positive when a rapid movement of the whole body of the animal was clearly noticed. Thereafter, the mice underwent auditory brain stem response (ABR) testing with broadband clicks. The presence or absence of Preyer's reflex was compared with the corresponding ABR thresholds. Five of the 46 animals studied (11%) showed a negative Preyer's reflex, while the remaining 41 animals demonstrated a positive Preyer's reflex. There was no difference between the abilities of the two different stimuli to elicit a Preyer's reflex. The click-evoked ABR thresholds in the test animals varied between 8 and 136 (mean 50) dB sound pressure level (SPL). Preyer's reflex was positive in all animals with an ABR threshold of < or = 76 dB SPL, but was absent in animals with an ABR threshold of > or = 81 dB SPL. Preyer's reflex is effective for identifying profound sensorineural hearing loss in experimental mice, but is insensitive for detecting less severe auditory dysfunction. For definitive hearing assessment, and for defining the hearing thresholds. objective electroacoustical methods such as ABR should be used.