Both descriptive and longitudinal studies of aging are nowadays a subject of growing interest in different countries worldwide. However, in Poland and other Central–Eastern European countries, such comprehensive, nationally representative, multidimensional studies were never performed in the past in elderly population. The present paper describes the PolSenior project including its objectives, sample selection and structure, methods, fieldwork procedures and study flow. The aim of the project was to examine medical, psychological and socioeconomic aspects of aging in Poland. The research sample included 5695 respondents (2899 males and 2796 females) split into six equally sized age groups of elderly individuals (65–69 years, 70–74 years, 75–79 years, 80–84 years, 85–89 years, 90 + years) and one group of subjects just about to enter old age (55-59 years). Subjects were recruited using three stage stratified, proportional draw. The response rate was 42% and ranged from 32% to 61% between provinces. The study consisted of three visits performed by trained nurses including questionnaire survey, comprehensive geriatric assessment and blood and urine sampling. The questionnaire consisted of medical and specific socioeconomic questions. The comprehensive geriatric assessment included blood pressure and anthropometric measurements, as well as selected scales and tests routinely used in the examination of elderly subjects. Blood and urine samples were collected from 4737 and 4526 individuals, respectively. More than 50 biochemical parameters were measured, and DNA was isolated and banked. In a selected group of 1018 subjects, a medical examination by a physician was performed. The self-rated health was lower in females than in males in age groups 70–84, but similar in individuals of both sexes aged 65-69 and 3 85 years. Besides providing data on health and functioning of elderly population, the PolSenior project aims to analyze interrelationships between different elements of health and social status, and between genetics and health status in advanced age. The results of the PolSenior project will facilitate prioritizing the state's public health and social policies in elderly population. Such a program provides also an excellent starting point for longitudinal studies and a basis for comparative analysis between Poland and other European countries or regions.