This work investigates the reliability of marine shell for radiocarbon dating New Zealand prehistory. Paired charcoal and marine shell radiocarbon ages from archaeological sites excavated for this study and from already dated archaeological contexts are compared, and two issues are considered: first, factors which can affect the radiocarbon dating of marine shell and charcoal samples; second, the effect of using either of two marine shell calibration methods in the comparison of marine shell and charcoal radiocarbon dates. A critique of the two methods available for calibrating marine shell radiocarbon ages is undertaken to examine the effect of each on age calibration, and in the comparison of marine shell and charcoal radiocarbon ages. In light of the results of the research, the time of colonisation of New Zealand is proposed based on archaeological sites with acceptable charcoal and marine shell radiocarbon chronologies.