The Hauraki Goldfield gold-silver deposits have produced more than 12 Moz of gold and 52 Moz of silver from some 50 quartz vein deposits of different size. The deposits were formed from hydrothermal fluids associated with volcanism from ~18 to ~2 million years ago. The active geothermal systems of the Taupō Volcanic Zone to the south are considered modern analogues, with deeply circulating meteoric water heated by magma bodies at depth. The resulting hydrothermal fluid reacts with wall rocks on ascent to the surface eventually depositing the gold and silver plus other metals from boiling and/or mixing with groundwater. Based on the analogy, the magma can also supply CO2, H2S and other constituents including metals. The extent of magmatic supply may influence the metal budget and if recognisable, may provide an indicator of prospectivity in exploration. Postulated indicators of magmatic input may include: 1) close spatial and temporal association with porphyry style mineralisation (e.g. Thames gold-quartz veins with the Ohio Creek porphyry copper prospect and its advanced argillic alteration at Lookout Rocks); 2) an ore mineralogy with telluride-bearing minerals, especially bismuth tellurides (e.g. Thames and Tui); 3) high salinity fluid inclusions in vein minerals (e.g. Waihi and Tui sphalerite), 4) sulfur isotope values for sulfides of near 0 per mil; 5) lead isotope values of galena (PbS) (e.g. Coromandel and Tui); 6) positive gravity anomalies (e.g. Waihi); and 7) the abundance of metals deposited (e.g. Thames, Karangahake and Waihi). None of these criteria are definitive, each having possible alternative interpretations. However, the high salinity fluid inclusions in sphalerite (ZnS) at Tui and Waihi are the most convincing for a magmatic fluid contribution during mineralisation. When the various factors are considered cumulatively, we suggest that magmatic fluids have contributed to the mineralisation of many of the gold-silver deposits of the goldfield.