As yet, there is no staging system for amyotrophic lateral sclerosis (ALS). One early attempt to define disease stages consisted of post-hoc analysis of the international, placebo-controlled, clinical trials of riluzole. In this analysis, five health states were defined for ALS (mild, moderate, severe, terminal, death) to determine whether therapeutic intervention with riluzole could favorably influence the time spent in the different stages. The time spent in the mild and moderate disease states (taken together) was considerably longer in patients treated with riluzole than in those treated with placebo (317 days compared with 242 days). Riluzole did not influence the median time in the mild, severe, or terminal ALS stages but did slightly shorten the time in the moderate ALS stage compared with placebo. In all the ALS stages, the 75th percentile of time in that state appeared to be extended. Survival analysis indicated that the relative risk was less than 1.0 with riluzole treatment in the moderate, severe, and terminal health states but not in the mild health state, when it remained at 1.0. The time to failure was longer in patients in the moderate, severe, and terminal ALS stages but was significantly longer only in the moderate ALS stage. These findings indicate that future studies of therapeutic intervention should examine rigorously defined stages of disease to examine end points other than death. The development of a staging system, analogous to the ones used in oncology, has implications for the concept of early diagnosis.