We report hairball in two young rabbits. Case one was a two-month-old male rabbit suffering from lethargy, anorexia, and constipation. On X-ray photographs, a slightly dense shadow was seen in the stomach area. Nosotropic treatment was performed, but the animal died on day 13. Necropsy revealed a ruptured stomach and a hairball in it. Case two was a five-month-old female rabbit suffering from lethargy, and anorexia. X-ray photography with contrast media injected into the stomach showed an enlarged stomach and the contrast media would not move into the duodenum even 90 minutes after injection. Laparotomy showed an enlarged stomach, and gastrotomy was performed. At the pylorus, a large hairball was present, which was removed. After the surgery, there was remarkable improvement and the rabbit has been in good condition since. High-protein-low-fiber diet, stress, and pregnancy are known to contribute to the development of this disease. Both rabbits had been on a diet of dry pellets. The first rabbit had experienced an environmental change 20 days before he became sick, and the other was pregnant. These cases indicate that even very young rabbits can be afflicted by this disease when they are exposed to various kinds of stress.