The 50 patients in this survey were classified by a panel of neurologists into 4 clinical sub-groups: Group Ia ("typical" Friedreich's ataxia, complete picture), Group Ib ("typical" Friedreich's ataxia, incomplete picture), Group IIa ("atypical" Frriedreich's ataxia, possible recessive Roussy-Levy syndrome), Group IIb (heterogeneous ataxias). The clinical symptoms and signs were analyzed for each of these groups. A constellation of signs constantly present in Friedreich's ataxia and obligatory for diagnosis was described. Other important symptoms, such as the Babinski sign, kyphoscoliosis and pes cavus were found to be progressive, but not essential for the diagnosis at any given time. Finally, a host of other symptoms can only be called accessory. The progression of scoliosis was found to be an important tool in the differential diagnosis of ataxias. Our study also indicates, in contrast to the opinion of some authors, that absent deep tendon reflexes in the lower limbs and early dysarthria are essential in "typical" Friedreich's ataxia.