Last year's podium finishers return in compatriots Terenzo Bozzone and Dylan McNeice.
Bozzone has finished second four times, and the 30-year-old believes he now knows what it takes to reach the top.
"In any ironman race you are bound to have those really tough moments and it is understanding how to deal with those bad patches and knowing that you will come through the other side that is key. Cameron Brown has that nailed. I just have to back myself."
McNeice believes he has learned from his podium finish last year, working hard with coach Tim Brazier to improve his bike strength.
"If I can get off the bike in a good place and if the run legs are there I'm in with a good shot."
Internationals are set to pounce.
Frenchman Cyril Viennot was fifth at Hawaii in 2014 and sixth last year, along with victory in Ironman UK and the ITU World Long Distance title.
Exciting American Matt Hanson ran 2:47 to win Ironman Chattanooga in a course record and set a course record 8:07 to win in Texas last year.
Watch for Australian Paul Matthews who was sixth on debut at Melbourne in 8:05 three years ago followed by runner-up at Arizona. He returned in 2014 to clock 8:02 to finish runner-up at the Ironman Asia-Pacific Championship.
American Meredith Kessler will return to her home away from home to chase her fifth straight win.
The Californian has formed a close affinity with Taupo, and zeros in on the record of six titles of Kiwi legend Jo Lawn.
"The course just makes my heart sing," said Kessler, the women's course record holder. "A cool, clear fresh water swim in gorgeous Lake Taupo, rolling bike terrain on a tougher chip seal and a run along the shoreline to streaming fans of people."
Like the men, the podium from last year is back in the form of Kiwis Gina Crawford and Melanie Burke.