Comparison of the average performance by 99 patients with multiple sclerosis (MS) and 32 healthy controls on the Selective Reminding Test (SRT) suggested that the patients' memory deficits arose primarily from difficulties in retrieving information from long-term storage. However, six different cluster analysis methods indicated three distinct patterns of SRT performance by patients, emphasizing the heterogeneity of memory function in MS. Approximately 25% of the patients performed normally while about 22% exhibited a severe amnesia-like disturbance. The remaining patients (53%) showed mild to moderate memory impairments, but only two patients met strict operational criteria for "pure retrieval failure".