Florence Nightingale Hospital is a 300-bed, university-affiliated, private medical centre with a large open heart surgery programme in Istanbul, Turkey. In this study, the mortality rates, lengths of stay (LOS) and extra costs of patients with deep sternal surgical site infections (DSSSIs) and superficial sternal surgical site infections (SSSSIs) following coronary artery bypass grafting (CABG) were determined from January 1999 to December 2002. Group I included 52 patients with DSSSIs, Group II included 36 patients with SSSSIs and Group III included 88 controls. The controls were selected at random from patients operated within the same year, with the same sex and age within five years, but who had not developed infection. Mortality rates in Groups I, II and III were 19.2%, 0% and 4.5%, respectively; the mortality rate in Group I was significantly different from that in Groups II and III (P<0.005). LOS was 47, 33 and 12 days for Groups I, II and III, respectively, and LOS was statistically different for each group (P<0.005). The costs of extra LOS, antibiotics, and radiological, microbiologial and other laboratory examinations for Groups I and II were US$6850.93 and US$3740.58, respectively. Both DSSSI and SSSSI following CABG extended the LOS and increased the cost, and DSSSI was significantly associated with a high mortality rate. These results suggest the need for improved infection control measures to reduce SSSIs following CABG. As an important component of the extra cost is the extra LOS, it is essential to shorten this period. This may be particularly applicable in patients with SSSSIs.