A solid-phase preparation, designated by the authors "plasma pencil", has been developed for rapid measurements of plasma-agglutinating and plasma-coagulating activities of microorganisms. Plasma pencil employed instead of liquid plasma is economic, ready-to-use, may be stored for a long time, makes the procedure more rapid and simple. Measurements of the aforesaid activities in 388 staphylococcal clinical strains, carried out with the use of this pencil, have demonstrated a high efficacy of the preparation; the results coincided with those obtained by the routine methods.