We report the one-year assessment of plasma exchange (PE) versus control in Guillain-Barré syndrome (GBS), based on a randomized multicenter clinical trial of 220 patients with GBS. Treated patients received four PEs, with either albumin or fresh frozen plasma (FFP) as replacement fluid. This study completes the short-term analysis previously published (Ann Neurol 1987;22: 753-761). Long-term benefit from PE was observed, as demonstrated by full muscular strength recovery at one year: 71% in the PE group versus 52% in the control group (p = 0.007), confirmed after adjustment for four prognostic factors. FFP showed no additional benefit compared with albumin (77% full recovery in the FFP group versus 65% in the albumin group; p = 0.22). PE did not affect the incidence of severe motor disability (11% in both groups).