Canterbury rider Anton Cooper (16) is expected to win the 47km Motatapu mountain bike ride from Lake Wanaka to Arrowtown today.
The Christchurch Boys' High School pupil was runner-up to the experienced Marcus Roy (Te Anau) in last year's Motatapu event.
Cooper is entered for the junior men's event and is also expected to be the overall winner.
Other juniors Alex Dodds and Marcus Jones could be close to the front in the men's race.
Roy set the race record for the event in 2008 with a time of 1hr 57min 47sec.
Cooper was only 41sec short of the record when he rode a time of 1hr 58min 28sec last year.
The bright hope of New Zealand mountain biking, he won the under-19 title at the New Zealand championships in Dunedin last month by 5min 4sec and has set his sights on the 2016 Olympics in Rio de Janeiro.
The established Motatapu 47km mountain bike race and companion off-road running marathon of 42.2km share a course from Lake Wanaka to Arrowtown.
A capacity field of 2000 mountain bikers and close to 1000 marathon runners will compete today.
Kath Kelly, of Millers Flat, (38) set the women's mountain bike record last year in a time of 2hr 20min 5sec.
Kelly is competing in the women's aged 30 to 39 grade.
The elite women's grade is expected to be won by Hannah Yeats, who set the junior women's record last year with a time of 2hr 36min 47sec.
Alexandra Williams (Christchurch), the defending champion, is expected to win the women's 42.2km marathon run again.
Her time last year was 3hr 25min 31sec.
Two notable entrants in the masters women's races are former world squash champion Susan Devoy and veteran women's marathon runner Kathrine Switzer (United States), who was instrumental in getting the women's marathon included on the Olympic programme in 1984.
There is also a shorter 15km run over the Motatapu Miners Trail, and the two-person team event, which was introduced last year and follows a different, more challenging 49km route over the Doc Motatapu track.
It is not a relay and both runners must complete the course.
The course features four major climbs totalling 2790 vertical metres and follows a marked track that will test the navigation skills and pace judgement of the runners.
It was won last year by the team of Darren Blackhurst (Arrowtown) and Chris Dagg (Queenstown) in a time of 7hr 25min 6sec.
A triathlon will be held for the first time this year.
It will begin with a 5km swim in Glendhu Bay before the 47km mountain bike ride from Glendhu Bay to Arrowtown through three high country stations, and ends with a 15km mountain run over the Miner's Trail.
It is limited to 50 competitors this year.
Motatapu
The facts
• First race: 2005.
• Distances: Mountain bike (47km), marathon run (42.2km), miners trail run (15km), two-person run (49km), triathlon (5km swim, 47km mountain bike, 15km run).
• Records: Mountain bike: Marcus Roy, 1hr 57min 47sec (men); Kath Kelly, 2hr 20min 05sec (women).
• Run: John Winsbury, 2hr 38min 13sec (men); Melissa Moon, 3hr 19.56sec (women).
