This is a review of coagulation disorders in elective surgical patients. The study represents both a personal experience in unusual bleeding and clotting disturbances and, in addition, a 15‐year review of unique problems evaluated by the Coagulation Department of a local general hospital. Of this group of cases, 17 were selected to illustrate the purpose of this report. Potential “bleeders” due to coagulation defects may be missed preoperatively both by history and by commonly accepted screening tests. The incidence of this situation is fortunately rare, but unfortunately this dulls the likelihood of early diagnosis with the initiation of specific treatment measures. The limitations of preoperative screening tests were apparent and should not be considered a fail‐safe detector of coagulation disorders. Qualitative and quantitative factor assays are the cornerstone for accurate diagnosis and a guide for specific replacement therapy. Although most surgeons will never have an in‐depth knowledge of hematology, the importance of having some fundamental awareness is apparent. This study encourages surgeons not to take the hemostatic mechanism for granted, and to see the need for understanding hematologic diagnosis and treatment.