Swiss duo Paul and Martin Laciga upset Brazil's Benjamin Insfran and Marcio Araujoin in the second round of the men's beach volleyball competition.
The Swiss brothers defied the heat to play a steady game of defence and beat the second seeds 21-19 19-21 15-12.
They will now play top-seeded Brazilians Ricardo Santos and Emanuel Rego in a quarter-final match-up.
Germany's Andreas Scheuerpflug and Christoph Dieckmann beat Andrew Schacht and Joshua Slack of Australia.
Scheuerpflug and Dieckmann will now play Australia's Julien Prosser and Mark Williams, who overpowered South Africa's Colin Pocock and Gershon Rorich 21-14 21-10.
In the women's event, Americans Misty May and Kerri Walsh beat China's Tian Jia and Wang Fei and they next face Canada's Guylaine Dumont and Annie Martin.
Americans Holly McPeak and Elaine Youngs also reached the last eight, after beating Sona Novakova and Eva Celbova of the Czech Republic 21-16 21-16.
Their next opponents will be Germany's Stephanie Pohl and Okka Rau.
Brazil's top women's teams face each other in the
quarter-finals after defending silver medallists Shelda Bede and Adriana Behar beat Bulgaria's Tzvetelina and Petia Yanchulova.
They will play twice Olympic medallist Sandra Pires and her new team mate Ana Paula Connelly.