Background: Discussions continue on the ideal priming fluid in adult cardiac surgery. The purpose of this prospective study was to evaluate the effects of different types of priming fluids on extravascular lung water, cell integrity and oxidative stress status., Methods: Thirty elective coronary artery bypass surgery patients were randomised prospectively into two groups. The first group received colloid priming fluid, while the second group received crystalloid priming fluid. Extravascular lung water index, advanced oxidative protein products, total thiol, free haemoglobin, ischaemic modified albumin and sialic acid levels were measured. Moreover, intra-operative and postoperative outcomes were reviewed., Results: There were no significant differences between the groups with regard to extravascular lung water index, oxidative stress parameters or cell integrity ( p > 0.05). Similarly, no significant differences were observed between the patients with regard to intra-operative and postoperative outcomes ( p > 0.05)., Conclusions: The presumed superiority of colloidal priming for cardiopulmonary bypass could not be confirmed in our study.