Background: Two recent publications have reported that a shorter interval between preoperative lymphoscintigraphy and sentinel node biopsy (SNB) is associated with improved survival of patients with primary cutaneous melanoma. The aims of this study were to analyse prospectively collected survival data for patients who had SNB on the same day as lymphoscintigraphy or the day after; and to assess tracer migration from sentinel nodes to second-tier nodes after lymphoscintigraphy on the previous day. Methods: Outcome data were obtained for patients who had lymphoscintigraphy and SNB on the same day (time interval less than 8 h) or the next day (interval more than 16 h). In a separate prospective cohort, same-day and next-day lymphoscintigraphic images of sentinel nodes and second-tier nodes were compared. Results: Following lymphoscintigraphy, 2848 patients had same-day and 3328 had next-day SNB. Survival outcomes did not differ between these groups. In a prospectively studied cohort of 30 patients, none had significant tracer migration from sentinel nodes to second-tier nodes on imaging the following day. Conclusion: No difference in survival after same- or next-day sentinel node biopsy is seen when 99mTc-labelled antimony sulphide colloid is used. This may be because of less tracer migration to second-tier nodes.