The directed TOCSY pulse sequence element transfers coherence predominantly into "forward-directed" antiphase coherences while simultaneously suppressing in-phase and "backward-directed" antiphase coherences. This novel selection principle, based on the "direction" of the target coherences, provides a new approach for the simplification of crowded spectra. In this article, the theory of directed TOCSY is presented for linear spin systems that are frequently found in carbon-labeled biomolecules.