This paper reports on 12 patients in a 3-year period (from 1st July 1980 to 1st July 1983) who were treated with artificial ventilation and with the muscle relaxant pancuronium bromide (Pavulon), over a period of 6 days or longer. After discontinuation of this drug these patients developed severe tetraparesis with areflexia, sometimes combined with disturbances of the extraocular and facial muscles and diffuse muscular atrophy, without sensory disturbances. Seven patients recovered completely after 2-5 months, two made an incomplete recovery and three died due to the primary disease. It is suggested that these neuromuscular complications were caused by prolonged high-dosage Pavulon treatment in combination with renal and hepatic disturbances and/or the use of aminoglucosides.