Hyper-IgM syndrome associating with severe neutropenie presenting in irregularis cycles was diagnosed in a 3-year-old male patient. His elder brother died of sepsis which appeared as a consequence of dysgammaglobulinaemia and neutropenia at the age of 9. We could not achieve a parmanent good result with the monthly immunoglobulin substitution and supportive treatment. The candida infection of the gingiva and of the oral mucous membrane expanded to the esophagus resulting in its complete occlusion and temporarily a gastrostomy was needed to feed him. We started with the recombinant human granulocyta colony stimulating factor (rh-G-CSF) treatment at the age of 6. We tried several ways of applying and finally the 10 micrograms/kg/dose given subcutan, for 5-10 days from the nadir of the neutropenic cycle seemed the most effective. The rh-G-CSF treatment resulted in an increase of ANC and the complete resolution of gingivostomatitis. The incidents of infections, the requirement of antibiotics and the duration of hospitalisation were markedly reduced. The consequent improvement in his physical condition made it possible to finally resolve the esophageal stricture surgically. We have not observed any neutropenic cycle since the end of the 14 month rh-G-CSF treatment. Though the medicine was discontinued there has been no recidiva for more than 22 months.