The subject.Differentiation in the science of labor law is examined as a feature of its sources; it is named among the principles of the branch and features of the method of legal regulation. The article analyzes the formation and development of the doctrine of differentiation (with an emphasis on its foundations) in the science of Soviet labor law, as well as modern problematic aspects of differentiation in labor law. Alongside the traditional division of the grounds for differentiation into objective and subjective, in the modern science of labor law it is proposed to conduct it on the basis of the structure of the employment relationship and the factor of working conditions. Subjective differentiation is proposed to be associated not only with the personal characteristics of citizens who are the subjects of employment legal relations, but also with the individual characteristics of the employer.Purpose of the study. It is proposed to specify the criteria according to which the grounds for differentiation are divided into objective and subjective ones (whether the need for special regulation is dictated by the specifics of work or is related to the special qualities of an employee). In addition, proposals are made to improve labour law in order to ensure the effective protection of labour rights.Methodology.The research was carried out with the application of the formally legal interpretation of legal acts as well as the comparative analysis of Russian and European legal literature. Method of rather-legal analysis are also the basis of the research.The main results.Thus, the criterion at the foundation of classification of differentiation factors of labour law norms is fairly obvious: whether the need for special regulation is dictated by the specifics of work (that said it does not matter which person will perform it) or whether the specificity of legal regulation is related specifically to the special characteristics of the employee and will appear regardless of the nature of his work.Consequently, employee's loss of special status entails termination of the specific rules of labour law, regardless of the will of the employer. At the same time, it is advisable to amend the Labor Code of the Russian Federation by establishing the obligation of the employee to inform the employer of such legally significant changes within a reasonable time. At the same time, the norms establishing benefits in respect of such employees should cease to be effective from the moment the employee loses his/her special status (e.g. due to removal of disability, termination of powers as a member of an election commission or member of an elected body of a trade union), while the rules imposing additional obligations and restrictions on the employee may be linked to the moment the employee notifies the employer.Conclusions.The authors clarified the criteria for classification the grounds for differentiation in labour law and, as a result, proposed amendments to labour law.