Coagulative changes at the height of serum disease were investigated i
n 28 patients with severe diphtheria. It was found that on day 10 afte
r first injection of diphtheria antitoxin hemocoagulation underwent ac
tivation with prevailing thrombogenesis coinciding in time with acute
period of serum disease. The severity of serum complications correlate
d with the degree of coagulation activity. A relationship exists betwe
en the amount of the given antitoxin, duration of hormone therapy and
occurrence of serum complications. There were specific for serum disea
se biochemical alterations indicative of destruction of blood cells an
d vascular-endothelial structures on the disease day 12-14.