To identify predictive and associated factors for muscle and joint pain in postpoliomyelitis syndrome (PPS).Cross-sectional study design.Postpolio clinics.Baseline data on 126 PPS patients entered into a multicentered clinical trial.Not applicable.Adjusted odds ratios were computed by using logistic regression modeling. Patients with or without muscle or joint pain were compared with regard to predictors and associated factors.In multivariate analyses for muscle pain, significant predictive and associated factors were female gender (P=.0006), longer duration of general fatigue (P=.019), and a lower score on the general health scale (P=.009) of the Medical Outcomes Study 36-Item Short-From Health Survey (SF-36). In multivariate analyses for joint pain, significant predictive and associated factors were female gender (P<.003), longer latency (duration of stability after polio; P=.008), younger age at interview (P<.002), greater weakness at acute polio (P<.07), weaker lower-extremity muscle strength (P<.04), and a lower SF-36 general health scale score (P<.02).Women are more likely to report muscle and joint pain in PPS. Greater initial motor unit involvement and lower-extremity weakness may be additional important factors for determining joint pain. Both muscle and joint pain are associated with reductions in quality of life.