This study sought to prospectively assess which factors were related to short-term worsening heart failure (HF) leading to or not to hospital admission, in long-term outpatients followed by cardiologists. The subsequent decision-making process was also analyzed. The study population consisted of 2,701 outpatients enrolled in the registry of the Italian Network on Congestive Heart Failure (IN-CHF) and followed by 133 cardiology centers (19% of all existing Italian cardiology centers). Clinical and follow-up data were collected by local trained clinicians; 215 patients (8%) had short-term decompensation (on average 2 months after the index outpatient visit). Multivariate analysis showed that previous hospitalization, long duration of symptoms, ischemic etiology, atrial fibrillation, higher functional class (New York Heart Association classification III to IV), higher heart rate, and low systolic blood pressure were independently associated with HF destabilization. Poor compliance (21%) and infection (12%) were the most frequent precipitating factors, but a precipitating factor was not identified in 40% of the patients. Poor compliance was more common in women, but no other clinical characteristics emerged as being related with a specific precipitating factor. Fifty-seven percent of the patients with a short-term recurrence of worsening HF required hospital admission; infusion treatment with inotropes and/or vasodilators was necessary in 19% of them. Long-term therapy was changed in 48% of the patients. Thus, in ambulatory HF patients, short-term worsening HF can be predicted according to the clinical characteristics on an outpatient basis. Nearly 1/3 of precipitating factors can be prevented. Patient education and avoidance of inappropriate treatment may reduce the number of relapses.