Two cases of granulocytosis after cardiac surgery were treated successfully with a recombinant granulocyte colony stimulating factor (rhG-CSF). Case 1 was a 65-year old man who underwent a double valve replacement due to infective endocarditis. As his white blood cell counts decreased to 1, 000/mm³ on the 24th postoperative day due to long-term antibiotic therapy, 125μg of rhG-CSF was given intracutaneously for 7 days. White blood cell counts increased after the 27th postoperative day and reached 15, 500/mm³ on the 30th postoperative day. The patient became afebrile immediately after administration of rhG-CSF. Case 2 was a 70-year-old man who suffered pneumonia after aortocoronary bypass surgery. As his white blood ceell counts decreased to 2, 300/mm³ on the 21st postoperative day, 80μg of rhG-CSF was given intracutaneously for 7 days. He became afebrile after the 22nd postoperative day and his white blood cell counts increased 18, 200/mm³ on the 28th postoperative day. rhG-CSF not only increases white blood cell counts but also reduces infectious symptoms and therefore is effective in managing granulocytosis after cardiac surgery.