Great Britain carried on from their dominant Rio 2016 Paralympics performance by winning five medals on the opening day of the Para Cycling Track World Championships in the Brazilian city.
Two British athletes struck gold at Rio's Barra Olympic Park Velodrome as Katie Toft won the women's C1 3,000 metres individual pursuit on her debut at the competition.
Her compatriot Jody Cundy followed up by winning the men's C4 one kilometre time trial to claim his 14th career world title.
Cundy clocked 1min 4.579sec to claim gold over Slovakia's Jozef Mtelka, who was timed at 1:07.336, with bronze going to Jacob Waters of the United States with a time of 1:08.739.
The 39-year-old Briton has now gone unbeaten in world one kilometre events since 2006.
Jon-Allan Butterworth and Blaine Hunt added to the team's medal tally with respective silver and bronze in the men's C5 one kilometre time trial behind Spain's Alfonso Cabello Llamas, who clocked 1:04.748.
Butterworth was timed at 1:05.850, with Hunt on 1:07.326.
Toft beat China's Li Jieli to gold, clocking 4:41.945.
Megan Giglia was the fifth Briton to win a medal on the night, taking silver in the women's C3 individual pursuit in 4:21.413 behind Germany's Denise Schindler, who clocked 4:06.604.
Bronze went to Jamie Whitmore of the US, who recorded 4:16.114 to hold off Australia's Simone Kennedy.
"I have been really pleasantly surprised with the competition here," said Cundy, a double gold medallist at the Rio 2016 Games.
"So many volunteers and so helpful - it makes it feel like a proper major competition.
"To come here and ride as well as I did today feels very good.
"It's been a fantastic experience and it's just the first day."
The men's C1 individual pursuit went to Spain's Ricardo Ten Argiles, who clocked 3:52.222 in finishing ahead of Canada's Ross Wilson, who stopped the watches at 3:54.584 as bronze went to China's Li Ahangyu.
Canada's Tristan Chernove won the men's C2 individual pursuit in 3:44.385 over China's Liang Guihua who clocked 3:50.304.
Russia's Arslan Gilmutdinov recorded 3:49.618 to beat Australia's Darren Hicks - who ended in 3:51.306 - to bronze.
David Nicholas of Australia took gold in the men's C3 individual pursuit in 3:34.804, beating Diederick Schelfhout of Belgium, who finished in 3:38.934.
Joseph Berenyi of the US overcame Spain's Eduardo Santas Asensio for bronze, clocking 3:37.293.
Alyda Norbruis of The Netherlands won the women's C2 individual pursuit in 4:11.913 in front of China's Zeng Sini, who clocked 4:13.340, with bronze going to Colombia's Daniela Carolina Munevar Florez.
In the women's C4 500m time trial China's Ruan Jianping won in 38.437, with New Zealand's Katherine Horan earning silver in 39.932 and bronze going to Australia's Emily Petricola who clocked 41.409.
The women's C5 time trial went to Caroline Groot of The Netherlands in 36.575.
China's Zhou Jufang took silver in 38.324, with bronze going to Argentina's Mariela Delgado, who was timed at 38.689.
The 2018 Track Worlds include 171 athletes - 50 women and 121 men - from 30 countries competing across four days of competition.
The competition is the first at which athletes can collect ranking points towards the Tokyo 2020 Paralympics.
It is also the first World Championship in any Olympic or Paralympic sport to use a Rio 2016 venue.