The authors' purpose was to determine 30- and 180-day readmission and mortality rates for acutely decompensated heart failure patients receiving nesiritide in the emergency department observation unit. The authors conducted a retrospective evaluation of all patients admitted to the emergency department observation unit, stratified by nesiritide administration, from January 2002 to January 2004. Eligible patients had a primary diagnosis of acutely decompensated heart failure. Observation unit treatment was by previously published protocols, except for nesiritide administration, which was per attending physician choice. Of 595 patients, 196 (33%) received nesiritide. The crude and adjusted odds ratios comparing readmission rates and mortality rates of the nesiritide group with the control group failed to demonstrate significant differences at either the 30- or the 180-day endpoints. The use of nesiritide for acute decompensated heart failure in the emergency department observation unit is not associated with mortality or readmission differences compared with standard therapy alone.