The major plasma membrane proteins of rabbit neutrophils were characterized by SDS‐PAGE, surface iodination,125l‐concanavalin A binding, and detergent extraction. Neutrophil membranes were prepared which lacked significant intracellular contamination with good retention of protease‐sensitive proteins. The major protein and predominant Con A‐binding protein was as surface exposed, 140,000 D (gp 140) protein which was solubilized by nonionic detergents but not low ionic strength. Actin and myosin but not other cytosol proteins were prominently associated with the isolated membrane particularly in a Triton‐insoluble form.Membranes were also prepared from surface‐iodinated neutrophils previously stimulated with a chemotactic peptide or degranulated. The granule membrane enzyme alkaline phosphatase was incorporated into the plasma membrane fraction of degranulated neutrophils. However, the membrane proteins in the different membrane preparations were identical on SDS‐PAGE and autoradiography. Therefore, using these techniques, no major alterations in protein composition of the plasma membrane could be detected following stimulation or degranulation of rabbit neutrophils.