Evidence from recent studies suggests that writing may be an aspect of cognition capable of identifying impairments specific to patients with Alzheimer's Disease (AD). The precise nature and progression of the writing disorder, however, remains unclear. The current study assessed the central and peripheral aspects of writing among a sample of minimal, mild and moderate AD patients and a group of healthy elderly controls on a narrative description task. Comparisons of the two groups indicated that AD patients suffer from a primary impairment at the semantic level. Even those in the minimal stages of the disease could be differentiated from controls on measures of word finding and information conveyed. This semantic impairment was coupled with a secondary milder impairment in phonological processing. The prevalence of phonological errors increased, but no shift in error type (plausible/implausible) was identified as the disease progressed. In addition to the central impairments, patients evinced damage at the peripheral level. In the more severe stages, patients experienced more problems with letter formation and stroke placement and tended to rely upon the more simplistic writing form of print. The writing impairment in AD is multi-componential in nature and follows the pattern of cortical deterioration reported in the brains of AD patients.