Granulocyte-specific antigens defined by human alloantisera are clinically important in neonatal neutropenia, autoimmune neutropenia, transfusion reactions, drug-induced immune neutropenia, and poor response to granulocyte transfusions. Many different antigens have been defined by human alloantisera using different assays. Only antigens of the N system of Lalezari are commonly studied today. The composition and location of these antigens within the granulocyte membrane are not known, but work is now proceeding on those issues. It also appears that these antigens may have some structural or functional role in the granulocyte. Although many myeloid MoAbs have been developed, there are very few reports to establish whether these identify structures that are related to the N series of granulocyte antigens. However, these MoAbs can serve as excellent reagents for better understanding the granulocyte membrane. It appears that studies during the next several years will provide exciting information about the structure-function relationships in the granulocyte membrane.