Japan's Go Soeda and South Korea's Hyeon Chung progressed to the second round of the Citi Open on Monday after beating Darian King and Dudi Sela respectively.
Soeda encountered little resistance in his first round match against King, beating the Jamaican 6-2, 6-1 in 54 minutes.
Chung registered his maiden win in an ATP World Tour 500 event as he best Sela 6-2, 6-1. Chung broke Sela in the first game of each set and saved the only break point he faced to come out on top in 57 minutes.
Soeda will face Sam Querrey in the second round, while Chung will take on third seed Marin Cilic.
Goeda's compatriot, Yoshihito Nishioka, and Yen-Hsun Lu of Chinese Taipei were unable to progress past the first round, as they were beaten by Alexander Zverev and Ricardas Berankis respectively.
Other winners on the day were James Duckworth, Ruben Bemelmans, Victor Estrellaburgos, Donald Young and Teymuraz Gabashvili.