To investigate the psychometric properties of the German version of the CERAD-NP, neuropsychological deficits were compared between 49 patients with mild cognitive impairment (MCI), 80 patients with Alzheimer's disease (AD), 36 with major depression (MD), and 26 elderly controls. All participants were outpatients of the memory clinic of the Section of Geriatric Psychiatry, Heidelberg University. Diagnoses were established based on clinical examination, laboratory testing, neuroimaging, and routine neuropsychological testing according to the criteria of aging-associated cognitive decline (AACD) for MCI, NINCDS-ADRDA for AD, and DSM-IV for MD, respectively. All CERAD-NP subtests discriminated between controls and AD patients with the latter showing significantly (p< or = 0.05) lower test scores. The subtests verbal fluency and constructive apraxia differed significantly between mildly and moderately AD, while the subtests assessing declarative (epsisodic) memory performance showed only minor, non-significant differences between the respective groups. The LKB patients took an intermediate position between controls and AD patients with significantly lower scores in verbal fluency and declarative memory performance than the controls. When compared with the AD patients, MCI patients were significantly impaired in all subtests except constructive apraxia. Relative to the controls, the patients with MD showed a decreased episodic memory performance but no evidence suggesting an impairment in other neuropsychological domains. Our results indicate that the CERAD-NP is a psychometric instrument which allows a sensitive discrimination between mild and moderate AD, MCI, MD and healthy controls. However, sensitivity of discrimination between different stages of dementia varies with respect to the different subtest. While the subtest for episodic memory showed floor effects already for mild dementia, subtests for verbal fluency and constructive apraxia were able to discriminate even between more advanced stages of the disease.