The vasopressor angiotensin II regulates vascular contractility and blood pressure through binding to type 1 angiotensin II receptors (AT₁; refs , ). Bradykinin, a vasodepressor, is a functional antagonist of angiotensin II (ref. ). The two hormone systems are interconnected by the angiotensin-converting enzyme, which releases angiotensin II from its precursor and inactivates the vasodepressor bradykinin. Here we show that the AT₁ receptor and the bradykinin (B₂) receptor also communicate directly with each other. They form stable heterodimers, causing increased activation of Gα_q and Gα_i proteins, the two major signalling proteins triggered by AT₁. Furthermore, the endocytotic pathway of both receptors changed with heterodimerization. This is the first example of signal enhancement triggered by heterodimerization of two different vasoactive hormone receptors.