Severe congenital neutropenia (SCN) is an inherited disorder characterized by severe neutropenia and recurrent infections from an early age, with bone marrow showing a maturational arrest of granulopoiesis at the promyelocyte stage. Since the introduction of G-CSF therapy the prognosis for affected children has improved dramatically. We describe two patients with SCN who were clinically unresponsive to G-CSF therapy. The results of in-vitro colony assays from these two patients are presented together with the results from the mother of one of these patients who also has a chronic neutropenia, and a further child with SCN who responded to treatment with G-CSF.