Since the motor paralysis occurs in all motor systems in ALS, the clinicopathological findings and care of the patients living beyond the development of respiratory failure must be considered. We have divided the efferent motor systems into four groups, i.e., limb, bulbar, respiratory, and external ocular. In this study, 37 ALS patients were followed for more than two years with respirator, and the onset of motor paralysis in all four systems was observed in each patient. First, we classified the patients into three groups according to the number of paralyzed motor systems observed within six months from the onset of the first motor paralysis, and we discuss the patient's prognosis after the first motor paralysis. Twenty-one patients with paralysis of the respiratory motor system alone were categorized as respiratory paralysis-preceded type ALS (R-type ALS), four patients with paralysis of the bulbar motor system alone as bulbar paralysis-preceded type ALS (B-type ALS), and 12 patients with simultaneous paralysis of two or more motor systems as combined motor system paralysis type ALS (C-type ALS). The results showed that the prognosis of R-type ALS is slow progression and that of C-type ALS, rapid progression. Next, we investigated the time of occurrence of the first motor paralysis of the four motor systems in 37 patients, and we discuss the most vulnerable motor functions in ALS, i.e., the initial clinical presentations in ALS. The most frequent first motor paralysis was of the respiratory motor system, and the initial clinical manifestations in ALS were impairment of fine discriminating voluntary respiratory and limb motor functions. These findings could be explained by the rule of ALS involvements, according to which onto-genetically newer motor functions are lost earlier than the older ones. Based on the findings in this study, we concluded that ALS initially involves the ontogenetically new motor functions in "the first system" proposed by G. Holstege, whose anatomical structure is composed of pre-motoneurons and motoneurons in the brain stem and spinal cord.