We retrospectively analyzed 54 patients who died of head and neck squamous cell caricinoma regarding the process and duration of cachexia using the modified Glasgow Prognostic Score (mGPS). The patients were classified as having cachexia when the serum albumin level was less than 3.5 mg/dL and the C-reactive protein (CRP) level was more than 0.5 mg/dL. The number of patients with cachexia was eight (8%) at the first visit and 50 (93%) at the time of death. In the 50 patients, the median and average time of having cachexia was 59 and 95 days, respectively. Thirty-two of the 50 patients (64%) died within three months after the presence of cachexia was confirmed. In this study, the time of having cachexia was so short, then the policy of care should be converted from aggressive into supportive in patients classified as having cachexia. mGPS would be an accurate assessment tool for cachexia and ascertain the end stage of head and neck cancer patients.