Alzheimer's disease causes a progressive loss of semantic memory, one manifestation of which is a progressive language deficit. In order to delineate the relationship between cognitive processing deficits and language disturbance, word-word and picture-word lexical-decision priming tasks were administered to patients with mild dementia of the Alzheimer's type (DAT) (n = 6), very mild DATs (n = 7), and older normals (n = 23). The mild DATs differed from the other two groups in both tasks. When pictures were used as primes, significant identity priming was seen in the normals and very mild DATs, but not in the mild DATs. The mild DATs showed an aberrant pattern-responses significantly slower with picture primes than with nonsense primes in all three picture-word conditions. This may reflect residual inhibitory activity within a damaged associational network. In the word-word paradigm, the mild DAT subjects demonstrated significant priming both when the prime and target were identical (identity priming, e.g., dog-dog) and when they were semantically related (semantic priming, e.g., cat-dog). The other two groups showed no significant priming. These data reinforce other studies which have found that DAT subjects show a supranormal amount of word-word lexical-decision priming. This "hyperpriming" may occur due to partially degraded internal representations which benefit from priming more than intact representations (a cognitive crutch). Both paradigms thus exposed information-processing deficits which distinguished mild DATs from the other two groups. DAT-induced changes in selective attention are probably contributing to these results.