Some patients, such as Jehovah's Witnesses, refuse to use blood products, which can make it difficult to achieve the same outcomes as in the general population. The objective of this study was to determine whether clinical characteristics and surgical outcomes in Jehovah's Witnesses undergoing cardiac surgery are similar to those in other patients. Paired-group retrospective cohort study. All Jehovah's Witnesses undergoing cardiac surgery between January 1998 and September 2006 were included (n=59). Cases were matched on a 1:1 basis according to sex, age (5) years, year and type of surgery, and need for repeat surgery. Preoperative, intraoperative and postoperative data were analyzed. The mean age of cases was 62.5 (11.1) years with 57.6% being female. Some 30.5% had had at least one previous cardiac intervention. The clinical characteristics of the two groups were similar. Hemoglobin and hematocrit levels were higher in Jehovah's Witnesses both before (13.6 g/dL vs 12.9 g/dL; P=.01, and 40.7% vs 39%; P=.09) and after (11 g/dL vs 10 g/dL; P=.003, and 34.2% vs 30.7%; P=.001) surgery. Jehovah's Witnesses experienced significantly less bleeding, were intubated for fewer hours, and had shorter stays in both intensive care and the hospital. There was no difference in the rate of postoperative complications or mortality. The clinical characteristics of Jehovah's Witnesses were similar to those of the control group. The complication rate was also similar in these patients, though the number of hours of mechanical ventilation was less, 24-hour bleeding was less, and the hospital stay was shorter. Mortality was similar in the two groups.