The patient was a 76-year-old male with disturbance of consciousness due to cerebral infarction. He was found lying in his garden on July 30, 1990 and was immediately hospitalized. Central venous alimentation was started on the same day, because the patient was incapable of oral nutritional intake. Aspiration pneumonia developed on August 3. As Pseudomonas aeruginosa and Candida were detected by sputum cultures on August 20, antibiotics were changed to latamoxef (LMOX), 6 g/day, tobramycin, 180 mg/day, and fluconazole, 200 mg/day, from August 30. Macroscopic hematuria was noted after exchange of the urethral catheter. Hematuria gradually worsened, bladder tamponade occurred, and anemia had exacerbated with Hb decreasing from 13.4 to 8.7 g/dl and Hct from 39.1 to 26% on September 14, when the patient was referred to our department. Corresponding marked increases were observed in PT from 11.5 to 50.1 seconds and in APTT from 33.7 to 107.6 seconds. As the hematuria was suspected to be due to vitamin K deficiency hypoprothrombinemia induced by LMOX, its administration was discontinued on the day of the referral. Hematuria was alleviated from the next day, and PT normalized to 12.1 seconds and APTT to 36.6 seconds 3 days after discontinuation. The administration of vitamin K was started on this day, and hematuria disappeared 7 days after discontinuation of LMOX administration.