We will perform an open-label, parallel arm, controlled study of intrarenal nesiritide in 26 patients hospitalized with CHF. Patients will be admitted for CHF exacerbation and randomly but equally divided into treatment and placebo groups. Both arms will receive diuretics on admission as dictated by clinical need. They will then have an 8-hour diuretic-free period (overnight). Each arm will then have renal parameters (GFR, RPF, urine output, urinary sodium excretion) assessed using PAH and iothalamate. These parameters will be measured prior to administration of drug during period 1. Randomization will be performed via an interactive computerized call in program following completion of screening procedures and once patient has given informed consent.