We investigated in some detail the immunologic and procoagulant activation patterns in men and women with unstable (UA, n=26) versus stable (SA, n=40) coronary artery disease (CAD). Leukocyte activation and platelet-leukocyte complex formation were assessed by flow cytometry. Plasma markers of coagulation and inflammation were analyzed. Unstable patients displayed higher levels of platelet-leukocyte complexes (P<.001), of leukocyte CD11b (P<.01), and of T cell HLA-DR (P<.05) than healthy controls did. Female UA patients presented the highest degree of complexes. SA patients only differed significantly from controls with respect to HLA-DR (P=.02). UA patients had higher levels of C-reactive protein (P<.01), IL-6 (P<.001), IL-10 (P<.01), and soluble fibrin (P<.001) than did stable ones. Regarding P-selectin levels, 25% of SA and 50% of UA patients were above normal range. Again, UA women presented the highest marker amounts. As for soluble tissue factor, women had higher levels than men regardless of the severity of disease (P<.001 in SA). We conclude that in unstable coronary syndromes, there is an activation of both coagulation and inflammation that coincides with an increased activation of platelets and leukocytes. Cellular interactions may contribute to the systemic responses observed. Women have different patterns of cellular activation than men, indicating differences in pathogenetic mechanisms.