The aim of the study was to analyse pulmonary function and to identify reliable prognostic factors associated with respiratory abnormalities in a consecutive series of patients with multiple sclerosis (MS). Pulmonary function was evaluated by means of a battery of measures, including maximal voluntary ventilation, forced vital capacity, forced expiratory volume, in 71 consecutive patients with primary and secondary progressive MS. Respiratory impairment was common in MS patients, occurring in 63.4% of all patients, ranging from 82.9% in non-ambulatory patients (with EDSS score >6.5) to 35.7% in ambulatory patients (with EDSS score <6). Severity of illness and cerebellar and mental impairment were significantly negatively associated with basal pulmonary function. Coordination plays an important role in determining respiratory abnormalities: respiratory abnormalities were found in 27 out of 32 patients (84.4%) with severe cerebellar impairment. The presence of severe cerebellar signs was associated with a very high risk of occurrence of respiratory impairment (O.R. = 6.24; 95% C.I. 1.71-22.82). Other significant variables were severity of illness (EDSS score > 6.5) (O.R. =4.71; 95% C.I. 1.42-15.66) and long disease duration (> 15 years) (O.R. = 3.39; 95% C.I. 1.01-11.42).