Roger Federer and Rafael Nadal won their first match as doubles partners.
The pair, who have 35 Grand Slam titles between them, won on the second day of the inaugural Laver Cup in Prague.
They beat Americans Sam Querrey and Jack Sock 6-4 1-6 (10-5) to give Team Europe a 9-3 lead.
Team Europe's players include world number four Alexander Zverev and seventh-ranked Dominic Thiem, while Nick Kyrgios and Denis Shapovalov, who impressed at the US Open, have represented Team World.