Organisers of the Shearwell Thame Summer Sheep Fair are hoping it will deliver £3 million in turnover this year.
The two-day fair, taking place on August 6 and 7, is one of the largest sheep sales in the UK.
It is organised by Thame Farmers Mart with entries for this year reaching 16,371.
Buyers from Wales are expected to return, following the lifting of bluetongue-related movement restrictions which impacted the fair last year.
This year's event will be senior auctioneer Simon Draper's final Summer Sheep Fair before he retires later in the year.
He said: “This is the 24th year of the fair, which has become the yardstick for the sale of sheep.
"With the prices we expect, even with fewer sheep, we could be touching a turnover of £3 million on the two days for this year’s fair."
Draper explained that Thame is known for the sale of early lambing Suffolks.
“This year we are going to show over 3,000 cross-breeding Suffolks, many of which normally go into Anglesey for early lambing.
“On the second day, we would normally be offering anywhere between 8,000 to 15,000 mule ewes and we have fewer this time because the cull ewe trade is so good," he said.
Draper went on to discuss prices, saying that at previous fairs, mules went for £209; whereas now the price is £230-£240.
He added: “We thought £169 for the ewes was a phenomenal sale price, but this year they are worth just as much for slaughter.”
Ahead of overseeing his final Summer Sheep Fair, Draper reflected on the growth of the event since it returned following the foot and mouth outbreak in 2001.
While this year's catalogue entries reflect the decline in the national flock, the fair remains one of the largest sheep sales in the UK.
He said: "When foot-and-mouth restrictions ended in 2001, we reinvented the fair and brought it back onto the farming calendar.
"A lot of people got in touch to thank us for doing so and, from there, it just grew and grew.
“At its peak, we were selling around 30,000 sheep in a single day, so we had to expand it into a two-day event.
The 24th Shearwell Thame Summer Sheep Fair takes place at Thame Showground (The Fair Field), Kingsey Road, Thame, OX9 3JL, on August 6 and 7.
Sales will commence at 10:00a.m on both days, with the ram sale beginning at 2:00p.m on Thursday, August 6.