This study examined the characteristics of asymptomatic worsening heart failure (HF) events and validated the role of a novel HF monitoring method (measuring body weight [BW] and percent body fat [BF%]) to identify such worsening HF events. A clinician determined worsening HF status by evaluating symptoms, physical signs, and pleural effusion on ultrasonography. A criterion of significant fluid weight gain was defined as BW gain ≥1.5 kg with a concomitant decrease in BF%. A total of 74 HF patients were included. During a mean follow-up of 20.8 months, 1588 visits were evaluated. A total of 79 worsening HF events occurred in 50 patients, in which worsening was symptomatic in 46 events (58%) and asymptomatic in 33 events (42%). Novel method eliminated 42 of 73 (58%) false-positive indications of worsening HF events based only on the BW criterion (≥1.5 kg) without excluding true worsening HF events. The test characteristics of this method in the diagnosis of overall HF events were sensitivity 65.8% (95% confidence interval [CI], 54.3–76.1), specificity 97.9% (95%, CI 97.1–98.6), positive predictive value 62.7% (95% CI, 51.3–73.0), and negative predictive value 98.2% (95% CI, 97.4–98.8). Preclinical fluid retention occurs frequently in established HF patients, and novel monitoring method can specifically identify preclinical worsening HF. Congest Heart Fail. 2012;18:37–42. ©2011 Wiley Periodicals, Inc.