The thesis deals with topics of internal communication with focus on its application in three particular companies. The main objective was to describe and evaluate the quality of internal communication, to analyze it and draw useful conclusions and practical recommendations to improve its efficiency. The basic concepts and specifics of information, communication, corporate culture and internal communication are presented and explained in the theoretical part, followed by an overview of the functions, goals, information flows and means of communication within the company. The assumptions of effective internal communication and related problems are accentuated. The practical part includes internal communication analysis based on a survey, qualitative interviews with managers, and company information available to the public. The thesis results in a detailed analysis of particular companies, their comparison, and specific recommendations for removal of the deficiencies and effective improvements