STUDY DESIGN: A retrospective study. OBJECTIVES: To evaluate the usefulness of postoperative suction drainage tip cultures as a method of predicting the development of deep wound infections after thoracolumbar surgery using pedicle screws. SUMMARY OF LITERATURE REVIEW: The primary diagnostic elements of post-operative spinal infections are a high degree of clinical suspicion by the surgeon combined with aspiration and culture of the suspected infection sites. MATERIALS AND METHODS: We analyzed the results of cultures on postoperative suction drainage tips from a total of 471 thoracolumbar surgery cases. We calculated the sensitivity, specificity, and predictive value and investigated the isolated pathogens. In addition, we performed quantitative analyses of serum C-reactive protein using Turbidimetry. RESULTS: The post-operative infection rate was 4.0%. The most common isolated pathogen of the true positive cases was staphylococcus aureus, which was found in 3 cases (methicillin-resistant staphylococcus aureus in 2 cases); and that of the false positive cases was coagulase-negative staphylococcus in 5 cases. The sensitivity of the suction drainage tip culture was 52.6%, the specificity was 96.3%, the positive predictive value was 37.0%, and the negative predictive value was 98.0%. In cases of C-reactive protein, true positive and false negative cases followed the same course, where the CRP decreased slowly for the first week but remained elevated persistently at the 14th postoperative day. CONCLUSIONS: Culture of the suction drainage tips could not predict the development of postoperative deep wound infections, but it had more significance in the exclusion of deep wound infections. We concluded that careful observation for other signs of deep wound infections are necessary when a clinically significant pathogens are isolated.