The sentinel node (SN) concept is not new, but its potential surgical application was not fully appreciated until the landmark report by Morton and Cochran et al. in 1992. It has since been confirmed that SN status in melanoma patients accurately reflects the status of the entire regional node field, and is a critically important prognostic indicator. However, randomized trials have yet to determine whether the SN biopsy technique is of any therapeutic value. With extended follow-up times, false-negative SN rates of up to 15% are being reported and presumably represent failures of nuclear medicine and/or surgery and/or histopathology. Innovative methods of increasing the accuracy of SN identification and of checking this retrospectively are being assessed. The next great challenge is to develop methods of SN assessment that are noninvasive yet are even more accurate than present methods. Techniques such as in vivo proton magnetic resonance spectroscopy hold great promise and suggest that this goal might be achievable.