The clotting screen is an ‘integral’ part of the routine blood tests in most medical wards. It is likely that only with the increasing requests for prothrombin time and activated partial thromboplastin time are abnormal results noted. Interpretation of these results requires good understanding of the coagulation system and problems with the laboratory analysis. Due to variable understanding of this complex system, many misconceptions have arisen in relation to the clinical effects expected from abnormal clotting screens. Some of these are discussed with considerations of appropriate management in those situations.