Based on the slope of speech intelligibility decline, 54 individuals with amyotrophic lateral sclerosis (ALS) were classified as fast or slow bulbar disease progressors. Following group assignment, the course of speech decline was modeled separately for these two subgroups. Fast progressors were characterized by a three-phase progression pattern with intelligibility declining at a progressively faster rate within each phase. Slow progressors were characterized by a consistent rate of intelligibility decline and thus, a single phase progression pattern. The approach used to identify fast and slow progressors may be useful in the future for stratifying patients enrolled in clinical trials. The subgroup-based models of intelligibility provide an empirical basis for making predictions about the timing of speech loss and the impending need for assistive communication.