Top seed Gael Monfils booked his place in the third round of the German Open in Hamburg after taking 72 minutes to cruise past Spanish qualifier Albert Ramos 6-4 6-2.
Second seed Jurgen Melzer also progressed with a 6-3 5-7 6-1 win over Daniel Gimeno-Traver of Spain while third seed Nicolas Almagro is also through after a 6-4 6-4 win over Czech lucky loser Lukas Rosol.
Among the seeds to fall was 11th seed Nikolay Davydenko, who went down 6-3 7-6 (7/5) to fast-rising German 20-year-old Cedrik-Marcel Stebe, who had beaten former world number one Juan Carlos Ferrero in round one.
Ninth seed Janko Tipsarevic was beaten 6-2 6-4 by Argentina's Juan Monaco and 16th seeded Spaniard Albert Montanes retired injured when trailing 6-1 3-2 to home favourite Philipp Kohlschreiber.
Italian 13th seed Andreas Seppi fell 6-1 7-5 to Czech veteran Radek Stepanek, who will next face Monfils. Eighth seed Fernando Verdasco won his all-Spanish match with Pablo Andujar 6-2 6-3.
German sixth seed Florian Mayer beat Turkish qualifier Marsel Ilham 6-4 7-6 (7/5), while 12th seeded Croatian Marin Cilic beat German qualifier Bastian Knittel 6-3 6-7 (4/7) 6-4.