Closure of the ductus arteriosus at birth is known to be related to the physiological rise in blood oxygen tension. Two main schemes have been proposed to explain the peculiar contraction of the ductus to oxygen, and their function is based on distinct sensor‐effector complexes. Specifically, these schemes comprise a cytochrome P450 monooxygenase‐endothelin complex or, alternatively, a mitochondrial redox mechanism‐voltage gated potassium channel complex. However, it is not clear how these systems may relate to the closure process. Here, it is proposed that they operate jointly within a single functional entity, with their combined activation being required for a full‐fledged contraction of the vessel to oxygen. This arrangement is thought to ensure a smooth transition from the powerful relaxant mechanism that is evident through the early postnatal period. Validation of this concept would not only settle a central question in the operation of the ductus but may also afford a broader perspective in any future translational research.