We previously defined "responders" as patients with increases in urine volume (UV) on day 1 after the administration of tolvaptan (TLV), and demonstrated that responders to TLV could be predicted with considerable accuracy by urine osmolality (U-OSM) levels. Responders and non-responders to TLV should be associated with different clinical courses after a certain time following TLV administration. Therefore, the aim of the present study was to validate our definition of responders by clinical parameters 1 week after administration of TLV. Data (n = 85) were obtained from in hospital patients with decompensated heart failure (HF) who had received TLV at 3.75-15 mg daily, and clinical data at 1 week after the administration of TLV were compared with those of baseline. Sixty patients (70.6%) were "responders", in whom UV on day 1 increased after the administration of TLV compared with day 0. "Non-responders" were older, and had higher serum creatinine concentration and lower baseline U-OSM than "responders". Serum creatinine concentration increased significantly in "non-responders", but was unchanged in "responders". Body weight, plasma B-type natriuretic peptide concentration, and HF symptom score decreased significantly in "responders", but remained unchanged in "non-responders". Increases in UV after the first administration of TLV were closely correlated with improvement of congestive HF after 1 week of TLV treatment, which verified our definition of "responders" to TLV.