Farmer Johnny Perkins, of Tuturau, near Wyndham, is organising the 30km back-country Ride to Recovery trek from Earnscleugh Station, Clyde, to Kawarau Station, Bannockburn, as a tribute to his late wife, Ava, who died of breast cancer.
Money raised from the November 22-24 ride will go to the Breast Cancer Foundation.
Mr Perkins said since announcing the ride three weeks ago, about 200 riders had asked for information and registrations were already coming in steadily.
Among those planning to attend were two Auckland women, who would hire horses locally, a group of seven from Cave, South Canterbury, and a male survivor of breast cancer.
Mr Perkins had planned to cap the number of riders at about 140, but said if more people wanted to participate, it would be possible to split the riders into two groups, with one group leaving about 30 minutes before the other.
The number of riders able to be accepted overall would depend on how many people would comfortably fit in the Kawarau Station woolshed, the venue for the Saturday evening dinner and auction, he said.
The organising committee would check that out soon before making a decision.
Riders will be encouraged to find sponsorship and Mr Perkins hopes the event will raise as much as $30,000 for the foundation.