A clinical follow-up of 12 patients with congenital nemaline myopathy (CNM) is reported. The aims of the study were to characterise the disease further, to investigate the prognosis of CNM and the factors influencing it, to find guidelines for treatment and, through neuropsychological tests, electroencephalography and computed tomography of the head, to determine whether the central nervous system is affected. The following distribution of muscular weakness was constantly found: the weakest muscles were the facial muscles, the flexors of the neck and trunk, the dorsiflexors of the feet and the extensors of the toes. The distal limb muscles and the limb-girdle muscles were clearly weaker than the proximal limb muscles. No signs of involvement of the central nervous system were detected, and IQs showed a skew towards higher levels. The clinical state of health had deteriorated in 10 of the 12 patients and improved in 2. In addition to the grade of disease activity, prognosis seemed to be influenced mainly by the development of scoliosis and by the restricted respiratory capacity. Since no specific therapy is available for this disease, recommendations for the management of CNM include active rehabilitation and vigorous treatment of respiratory infections. Physiotherapy should focus especially on the maintenance of cardiorespiratory capacity and the prevention and treatment of scoliosis. Long periods of immobilisation should be avoided.