Four families, 29 members, with Pendred's syndrome were studied to clarify 
hearing loss and hormonal status. The ages ranged from 3 to 50 years. Complete 
Pendred's syndrome was found in 9 patients. They had bilateral profound hearing 
loss with residual hearing at low frequencies. Goiter was diagnosed at the age 
of 1 to 14 years with a positive perchlorate discharge test. Twelve of the 
patients' relatives showed partial Pendred's syndrome. Mild sensorineural 
hearing losses occurred in the low- and medium-range frequencies with normal 
perchlorate discharge test results in 6 cases. The other 6 had a slight drop in 
the perchlorate discharge test results with normal hearing. Five subjects were 
normal and 3 had normal hormonal and normal perchlorate discharge test results, 
but were not tested audiologically. This paper shows that patients with 
Pendred's syndrome may have goiter at birth or develop it between 8 and 14 
years, that their deafness is bilateral and profound, and that their perchlorate 
discharge tests are positive. Relatives of Pendred's syndrome patients showed 
mild low-frequency sensorineural hearing loss without goiter and normal 
perchlorate discharge test results in half the cases, and a slight drop in the 
perchlorate discharge test results with normal hearing and without goiter in the 
other half. A correlation between these findings and genetic studies needs 
further investigation.