The purpose of this study was to investigate potential risk factors for failed sentinel lymph node identification in breast cancer surgery. Patient characteristics, tumour characteristics, surgeon experience and detection success/failure were registered at 748 sentinel lymph node biopsy procedures at our inpatient clinic. Data were analysed with backward stepwise multiple logistic regression with a cut-off point of p<0.05. We found that increased age, increased BMI, medial tumour location and less surgeon experience independently were associated with a lower sentinel lymph node detection rate. Tumour size, palpability and biopsy method were not significantly associated with the sentinel lymph node detection rate. In conclusion, it is possible to identify patients with a higher risk of sentinel lymph node identification failure and we recommend that these patients are operated by experienced surgeons in order to avoid accumulation of independent risk factors in individual cases.