(A) Neutropenia resolved after treatment with G-CSF in UPN10, the only patient who satisfied strict mathematical criteria for cyclical neutropenia, with an average periodicity of 23.3 days. Doses of G-CSF were steadily titrated down from 5 to 0.5 mcg/kg/day in order to keep ANC above 1.5 × 109/L (note logarithmic scale with ANC ranging up to 33.9 × 109/L). (B) By contrast, UPN69 continues to show irregular periods of neutropenia after commencement of G-CSF at 3mcg/kg/dose three times weekly. (C) Effect of G-CSF on range of ANC in 14 other patients (UPN 5, 8, 13, 19, 20, 23, 34, 38, 39, 40, 41, 44, 58 and 67) with the largest numbers of on- and off-therapy CBC.