Partial factors for carbon concrete. The design of structures is based on the semiprobabilistic safety concept with the separation of action and resistance sides. The determination of partial safety factors for concrete and reinforcing steel is mainly based on extensive experience. Thus, a generally accepted safety level is achieved. Corresponding experience is not available for new construction types such as carbon concrete. This results in a goal conflict for the determination of a partial safety factor. On the one hand, it must not be too low to achieve the required safety level, on the other hand not too high to ensure the economy of the design. The paper develops a methodically coherent approach for the determination of partial safety factors for construction types with few empirical values regarding their reliability. The knowledge of the statistical properties of the resistance side of the underlying design model is required. To determine partial safety factors, the semiprobabilistic resistance value is related to the probabilistic value according to a FORM approach. From this the so-called safety margin is derived as a measure of the safety level. The safety margins achieved with the proven reinforced concrete construction are used as a reference value to determine the partial safety factor for carbon reinforcement. The approach is illustrated using bending design with pure carbon reinforcement and mixed reinforcement, but is basically also applicable to other design situations.