A 10-year survey for serologic titers to brucellosis and leptospirosis in mule deer (Odocoileus hemionus), elk (Cervus canadensis), and antelope (Antilocapra americana) in Colorado is summarized. Over 10,000 blood samples were tested against Brucella abortus and 4,747 samples were tested against Leptospira pomona. A total of 1,761 blood samples were tested against L. canicola, L. grippotyphosa, L. hardjo, L. icterohemorrhagiae. All results were considered negative.