SummaryA 36 years-old man, suffering since more than ten years from a severe hemorrhagic recto-colitis (ulcerative colitis) experienced a bad relapse at the beginning of 1972. Treatment with Salazopyrin (Azulfidin) and ACTH proved of no avail. Because of a white cell count of 14,200 it was decided to resort to an anti-infectious therapy : Trimethoprim-sulfamide (Eusaprim) was given in daily amounts of 4 tablets for one week ; afterwards the daily dose was reduced to 2 tablets. Results were spectacular : within three days the diarrhea ceased ant there occurred only a minimal passage of blood after bowel movements. The left colon was no longer tender. Within the next five months the body-weight increased with 6 Kg.