Preview In patients with congestive heart failure, a diversity of neurohumoral and renal responses are involved in the maintenance of effective circuiting blood volume. The major clinical consequences of these responses are edema formation and, ultimately, decreased renal perfusion. In this article, the authors review the mechanisms that affect renal function in patients with systolic heart failure. A companion article on page 153 discusses use of therapeutic agents that modify these pathophysiologic sequelae.