Final results of an investigation into whether oxygen saturation of tissues (StO2, measured by spectrophotometry) could predict surgical site infections (SSI) after major abdominal surgery are presented. StO2 was measured on the arm and wound site pre-operatively and then at 12, 24 and 48 hours post-operatively. A Whitland Research RM200 was employed as the visible lightguide spectrophotometer. StO2 measurements using this machine were designated SSO2 (skin SO2). A Hutchinson Inspectra Model 325 was used for the near infrared spectroscopy (NIS) measurements. StO2 measurements using this machine were designated MSO2 (muscle SO2). Of 59 patients (38 males, 21 females), 42 healed uneventfully and 17 developed SSI. The overall infection rate was 28.8%. No significant differences were seen in wound SSO2 between outcome groups at any stage. At 12 hours there was a significant difference between the two groups with respect to mean wound MSO2 (A = 58.3 +/- 21.6%, B = 42.2 +/- 16.6%, p = 0.005, 95% confidence interval = 5.26, 26.98). A receiver operating characteristic curve showed that when a wound MSO2 of 53% was chosen as the threshold to classify potential infection a sensitivity of 71% and a specificity 73% (chi-squared test, p = 0.002) was achieved. The use of the near-infrared spectrophotometry as a tool to predict wound infections should be further evaluated and advocated.