To study prospectively the health status, and especially the physical functioning, of polio survivors with and without postpoliomyelitis syndrome (PPS), and to identify prognostic determinants of change in physical functioning.Prospective cohort study; measurements at baseline and after 1, 2, and 6 years.University hospital in the Netherlands.Seventy-six subjects with PPS and 27 without PPS.Not applicable.The Nottingham Health Profile (NHP) physical mobility category.Subjects with PPS had significantly poorer health status than subjects without PPS. No significant differences in mean NHP physical mobility scores between baseline and 6 years were found; both groups had improved after 1 year, after which there was a slow decline over the next 5 years. During the first 2 years, strength measurements showed little decline that was not related to changes in NHP physical mobility score. A physical performance test revealed no mean change in the first 2 years, but the subgroup with a decline above the 75th percentile eventually deteriorated 10.5+/-16.3 points on the NHP physical mobility category (P=.01) at 6 years from baseline. This subgroup had more extensive paresis than the other subjects, although it was not significant (P=.07). The extent of paresis at baseline was the only prognostic determinant for an increase in NHP physical mobility problems after 6 years.Subjects with and without PPS did not differ with regard to changes in health status in a 6-year period. The fact that the extent of paresis was a prognostic factor for a decline in physical functioning is in accord with a (slow) decline in muscle mass, as a late effect of polio, that may lead to a decline in physical functioning as the reduced muscle capacity becomes less able to meet the demands of daily physical activities.