A number of abnormalities in metabolic and biochemical processes have been found in cultured skin fibroblasts derived from patients affected by Alzheimer's disease (AD). An example of the successful use of peripheral cells to examine a cell biological abnormality in AD are the studies on transduction systems and on APP metabolism, mostly performed on fibroblasts from AD donors. In fact, some of the described alterations mirror events that have also been demonstrated to occur in the AD brain. Within this context data obtained using peripheral cells may help to identify and to test hypotheses on the primary pathophysiological mechanisms leading to AD. In perspective, the identification of peripheral biological markers could provide a useful aid in AD and could allow identification of stages of of the disease or subgrouping of patients, possibly helping to predict the response to treatment.