This pilot study examined the feasibility of monitoring changes in body weight and body-fat percentage (BF%) using commercially available digital weight scale incorporating bioelectrical impedance analyzer (HBF-352-W, Omron Healthcare Co, Kyoto, Japan) to estimate changes in body fluid status in definite heart failure (HF) patients during follow-up.A total of 64 patients completed a prospective study (June 2003-December 2006). During the study period, 38 patients developed worsening HF over a mean duration of 34 ± 3 days from the most recent visit with clinical stability to the time of worsening HF status. Of these, 32 patients (84%) showed an increase in body weight concurrent with a decrease in BF% during deterioration. During recovery (n = 35), all but 1 patient showed a decrease in body weight concurrent with an increase in BF%. Combined monitoring of both body weight and BF% provides quite excellent predictive accuracy (70%, 95% CI 59–81%) for identifying worsening HF status when compared with a sole body weight monitoring (56%, 95% CI 44–68%]) (cutoff point of body weight gain ≥1.5 kg).New monitoring method reported here is an effective tool for specifically detecting fluid weight gain at deterioration in definite HF patients.