Bronchorrhea, defined as watery sputum of 100 ml or more per day, was seen in a 52-year-old female patient with diffuse lymphangitic metastasis of colon carcinoma to the lung. For 5 months before the visit to our clinic, she complained of progressive worsening of the cough, watery sputum, and shortness of breath. On admission to our hospital, she expectorated large amounts of nonpurulent watery sputum (150 to 300 ml/d), and showed diffuse reticular and linear shadows in both lungs on chest radiograph and severe obstructive impairment (FEV1 percent, 35 percent) in lung function tests. Histologic findings obtained from both surgical specimens at abdominal operation for ileus and lungs at the autopsy revealed lymphangitic metastasis of ascending colon carcinoma to the lung. At autopsy, histologically the lungs showed diffuse infiltrations of mucus-secreting adenocarcinoma cells to both lung parenchyma and airway submucosa.