The objective of the investigation described in this paper was to develop a basic set of data required for the application of the strengthening method of bonding CFK strips as reinforcing elements to the existing reinforced concrete structures. In addition on the investigation aimed at establishing the dimensioning data, the work also focused on technical issues related to the design and execution in order to ensure the practical applicability of the method of externally bonded CFK strips. The CFK strips are placed on the bottom side or on the bottom part of the web. The paper also includes the description of variants of tested beams and the evaluation of experimental data, the conclusion, and the outline of elaborated variants.