We present a case of a 74-year-old Greek male who suffered from paraphasias, memory and orientation problems. The patient was assessed with neuropsychometric tests, auditory event-related potentials and cerebrospinal fluid proteins and was diagnosed with mild cognitive impairment. The emphasis on the case is on the unexplained high levels of P300 and Slow wave of the auditory event-related potentials. P300 is believed to be delayed in Alzheimer's Disease (AD), however in our case it was extremely prolonged in baseline and follow-up examinations without AD being diagnosed. This might suggest that AD is a complex and multifactorial disease.