A best-evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was 'Is a fully heparin bonded cardiopulmonary bypass circuit superior to a standard cardiopulmonary bypass circuit?' Altogether more than 792 papers were found using the reported search, of which 13 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated (Table 1). The studies analysed show that perfusion with heparin-coated and heparin-polymer-coated bypass does not increase the risk of adverse effects but reduces blood loss, re-operation rates, ventilation time, length of intensive care unit (ICU) and hospital stay and is also associated with improved biocompatibility, as evidenced by platelet preservation, reduced leucocyte and complement activation, and proinflammatory cytokine production. The various coated circuits have comparable biocompatibility as evaluated by a range of inflammatory markers and clinical outcomes. Three studies documented a significant decrease in post-operative blood loss (P = 0.001-0.54) and a meta-analysis found that perfusion with a heparin-bonded circuit resulted in a reduction in blood transfusion requirements (20%), ventilation time (P < 0.01), length of time in the ICU (P < 0.01) and also hospital stay (P = 0.02). Two studies found reduced levels of polymorphonuclear elastase (P < 0.018-0.001) and two trials concluded that the use of heparin-coated circuits in combination with low-dose systemic heparin (activated clotting time >250) resulted in the greatest clinical benefit and improvement in inflammation. One study documented significant platelet preservation with the use of third-generation heparin-polymer-bonded circuits (P ≤ 0.05). We conclude that despite heparin-bonded and newer third-generation heparin-polymer-bonded cardiopulmonary bypass circuits having a greater cost per person, their improved clinical outcomes and biocompatibility in patients undergoing cardiac surgery make them a preferable option to standard non-heparin-bonded circuits.