Background: Very little is known about the long term cognitive sequelae of bipolar disorder. Aim: To investigate neuropsychological functioning in older euthymic persons with early onset bipolar disorder. Method: Fifteen older patients (age >60) with an early onset (<50 years) bipolar-I disorder in a euthymic mood were tested using a comprehensive neuropsychological test battery. Neuropsychological functioning was compared with that of a sex, age and education-matched group of 15 comparison subjects without mood disorders or memory complaints. Results: Bipolar subjects scored lower than comparison subjects on selective attention, verbal memory, verbal fluency and mental effort tests. Conclusions: The findings suggest that euthymic bipolar patients are impaired across a range of cognitive domains. This could represent a trait-like cognitive disability related to the disease, as the impairments are comparable with those found in younger bipolar patients.