The scintigraphic examination with Tc-99m pertechnetate-labeled anti-NCA 95 antigranulocyte antibodies (AGAb) was performed in a 14-year-old boy with a 7-year history of poorly controlled ulcerative colitis to estimate the spread and activity of the disease. The disturbance of the splenic function was also suspected because Howell-Jolly bodies were present in the peripheral blood smears. High AGAb uptake in the rectum, sigma, and descending colon was observed on scintigraphy scans, indicating an active inflammatory process. Slight depression of hemopoiesis was also noticed. The spleen was not visible on the scans, although it was visible on ultrasound examination performed a few years earlier. Because of the refractory disease, total colectomy was performed. The spleen was not found on surgery. This case shows all benefits of using AGAb as a diagnostic tool. With a single injection we were able to show the spread and activity of the intestinal disease, distribution and function of the granulopoietic bone marrow, and absence of the spleen.