Aflatoxin was fed (0, .625, 1.25, 2.5, 5.0, and 10.0 microgram/g) to broiler chickens from day-old to 3 weeks of age when the birds were bled and intrinsic coagulation parameters measured. Clotting times of whole blood were increased by aflatoxin (2.5, 5.0, and 10.0 microgram/g) and decreased in blood samples activated by contact with the surface of crushed glass. There was no interaction of aflatoxin with the contact phenomenon. Partial thromboplastin times were significantly (p less than .05) prolonged by 5.0 and 10.0 microgram/g aflatoxin. Intrinsic activity as judged by whole blood thromboplastin generation was reduced nearly 40% by those two levels of aflatoxin. Activity analogous to human factor VIII was depressed by the two highest doses, but factor IX was significantly (P less than .05) reduced by only the highest dose fed, 10 microgram/g. These data suggest that chickens possess an intrinsic coagulation mechanism that is sensitive to aflatoxin but that the factor or factors responsible for the contact response are refractory to this important mycotoxin.