Recent data suggest that a proportion of patients with primary neuronal degeneration of the Alzheimer type have the HLA-B7 antigen. However, the possibility that other differences might exist between patients with and without the marker has not been examined. We tested a range of cognitive skills in Alzheimer patients with and without the HLA-B7 to examine whether those individuals with the HLA marker would exhibit a profile of cognitive loss different from those without it. Our results indicate that patients with HLA-B7 antigens had selective attentional scores that were significantly lower than Alzheimer patients without the antigen. Neither group was significantly different in either memory capacity or retrieval from short-term and long-term memory. The data support the hypothesis that there may be more than one disorder in what is now referred to as dementia of the Alzheimer type.