Sixteenth-seeded Philipp Kohlschreiber of Germany and Alexandr Dolgopolov of Ukraine won in straight sets in the first round of the Monte Carlo Masters on Sunday.
Kohlschreiber broke Brazilian Thomaz Bellucci's serve five times in a 6-4, 6-2 win, while Dolgopolov saved all three break points he faced in a 6-2, 6-4 win against Bernard Tomic.
Dolgopolov broke Tomic's serve to improve to 5-1 overall against the Australian. He faces fifth-seeded Juan Martin del Potro of Argentina in the second round.
Kohlschreiber plays either Frenchman Jeremy Chardy or a qualifier.
Later Sunday, Xavier Malisse of Belgium was playing Bulgaria's Grigor Dimitrov.
Top-ranked Novak Djokovic will later confirm whether he will take part in the tournament after twisting his ankle last weekend. He was included in the main draw.