We present a detailed analysis of the DFNA10 phenotype based on data from 25 hearing-impaired persons coming from a large American pedigree segregating for deafness at the DFNA10 locus (chromosome 6q22.3-23.2). Cross-sectional analysis of air conduction threshold-on-age data from all available last-visit audiograms (linear regression analysis, age over 15 years) showed progression of hearing loss at a rate of 0.6 dB/y over all frequencies, with a flat to gently sloping age-corrected threshold of about 50 dB. The results were significant at 0.25, 4, and 8 kHz, but only if corrections for presbycusis were not included. Longitudinal threshold analysis performed in 1 case, covering ages 6 to 32 years, showed progression of hearing loss at a rate of 2 to 3 dB/y over 0.25 to 8 kHz. Nonlinear regression analysis was performed on phoneme discrimination scores with use of sigmoidal dose-response curves with variable slope. On the basis of these data, the hearing loss phenotype in this American DFNA10 family can be described as postlingual, initially progressive, and resulting, without the influence of presbycusis, in largely stable, flat sensorineural deafness.