Introduction 1 2 3 4 5 4 6 9 10 13 14 20 Materials and methods This study was performed between May 2002 and May 2005 in five teaching hospitals and one university hospital. All procedures were supervised by one of the coordinating surgeons (Plukker, Braat). Only patients with histologically proven primary colon carcinoma were included in the study. Patients with distant metastases or gross lymph node involvement as shown by pre-operative examinations or palpation during surgery were excluded. The procedure was only performed when one of the study coordinators was available for supervision (Plukker, Braat, Kelder). The study was approved by the local scientific ethics committee, and all patients had given informed consent. Patients with rectal cancer were excluded from the study. 5 5 Definitions 1 Fig. 1 SLN pts  Results 1 1 Table 1 Tumour characteristics Characteristics Values Tumour location    Right colon 35  Left colon 2  Sigmoid colon 32 T-stage    1 1  2 14  3 48  4 6 Mean number of lymph nodes 11 Mean number of SLN 2.3 Discussion 2 14 21 15 18 20 14 17 21 17 14 20 21 Table 2 Study Number of patients Number of centres Identification rate (%) Accuracy (%) Sensitivity (%) Upstaging (%) 15 40 3 100 100 100 10 18 131 3 99 97 92 16 14 72 13 92 81 42 0 21 38 2 79 76 25 3 Kelder and Braat 69 6 97 96 89 13 or 18 15 18 20 22 6 8 23 24 9 24 5 15 18 20 1 1 12 25 26