The concentrations of the four major brain gangliosides--GM1, GD1a, GD1b, and GT1b--were determined in cerebrospinal fluid from 43 patients with "probable Alzheimer's disease" and 19 healthy controls. Alzheimer's disease was divided into type I (with the memory disturbances and predominant cortical parietal symptoms that are characteristic of Alzheimer's disease) and type II (with general cognitive and mild confusional symptoms, with or without only mild parietal symptoms). The GM, concentration was significantly higher in patients with Alzheimer's disease type I than in those with Alzheimer's disease type II and age-matched controls, but did not differ significantly between patients with Alzheimer's type II and age-matched controls. As gangliosides are enriched in nerve cell membranes, preferentially in synapses, the findings suggest more severe degeneration of cortical nerve cells in patients with Alzheimer's disease type I than in those with Alzheimer's disease type II.