Human activity is a deliberate and consciously organized activity of people in order to achieve some beneficial effect that can meet a certain kind of personal or common needs. Prekaraj is a term that is called a fairly heterogeneous group of people with regard to their social status and position in the labor market. Any form of non-standard work can be considered as a precarious work, a work that differs from the situation of a traditional employment model: a stable full-time job where the worker has one employer on whose order he works, the job is ongoing throughout the year and the worker expects to be employed indefinite and enjoy certain benefits and forms of insurance. The aim of this thesis is to show phenomenon, called by some authors, “new social classes” and to present the methodological problems of defining and investigating precarious work. Excessive, non-standard work, in most cases, was not chosen by the will of the workers and it is potentially dangerous, so it is important the role of the trade unions which should be more dedicated to the prevention of precarious work.