BACKGROUND Our goal was to specify the relationship between the level of activity (intellectual, physical, and social) in persons diagnosed with mild cognitive impairment (MCI) and the further progression of cognitive dysfunction. MATERIAL AND METHODS We examined 193 patients diagnosed with MCI (according to the criteria of the Working Group on Mild Cognitive Impairment) and under treatment at our Mental Disorders Clinic. It was assumed that these persons would remain under systematic psychiatric observation until dementia was diagnosed. The present study results from a seven-year observation period. The mini-mental state examination (MMSE), the Activity Scale (with the intellectual, physical, and social subscales), and the Instrumental Activities of Daily Living (IADL) scale were used to evaluate the participants' status at baseline. The MMSE was re-administered after one year and again at the end of the observation (either upon diagnosis of dementia or after seven years). At each meeting with the participant, the clinical diagnosis was verified to determine if the patient had dementia or not. Of the 193 people initially qualified for the study, 75 were available for the final analysis. RESULTS It was found that there was no statistically significant difference in the baseline MMSE scores between the persons with stable MCI and the persons who had progressed to dementia. However, statistically significant differences in the level of activity at baseline on both the global IADL scale and the Activity Scale between those with stable MCI and those who had progressed to dementia were found. These differences were manifested in the IADL subscales for telephone use, shopping, transportation, and personal finances, and in the physical activity subscale. CONCLUSIONS An evaluation of intellectual, physical, and social activity can be useful in determining the prognosis for the future course of MCI.