It is stated in this article that nursing is a professional science the goal being to utilize the nursing practice. New theories are formed or existing theoretical hypotheses are tested by nursing research. The difference between these two approaches is introduced. Nursing research for health promotion, prevention from illness and rehabilitation is discussed. The subject is viewed by the basic concepts of nursing: person, environment, health, nursing interventions. It seems to be essential to develop nursing theory for practise. It means to accept the point of view in which clinical nurses are theorists like academic researches.