There were no shocks at the Fayez Sarofin and Co Championship on Tuesday as the big names made it through.
Feliciano Lopez (five) and Leyton Hewitt (seven) were the only seeds in action in Houston, with the former winning against Robby Ginepri and the latter against Peter Polansky.
Lopez had an easier time of it than Hewitt, though, winning 7-5 6-2 as the Australian went all the way before winning 6-4 3-6 6-4.
Donald Young was the day's most impressive performer as he dropped just one game in a 6-0 6-1 win over Ryan Harrison, while there were also wins for Benjamin Becker, Michael Russell and Steve Johnson.
Meanwhile, Sloane Stephens was a surprise first-round casualty at the Copa Open Colsanitas on Tuesday, losing to Mariana Duque-Marino.
The second-seeded American was a 6-3 6-3 loser to the Colombian, who was a popular winner on home soil.
The fourth seed also went home on Tuesday, with Anna Schmiedlova going out to Irina-Camelia Begu 6-3 6-1.
Number five seed Caroline Garcia survived, though, seeing off qualifier Florencia Molinero for the cost of seven games, with Paula Ormaechea, the seventh seed, also through against Patricia Mayr-Achleitner.
Elsewhere there were victories for the likes of Romina Oprandi and Danka Kovinic, qualifier Lara Arruabarrena, lucky loser Sofia Shapatava and wildcards Maria Irigoyen and Yuliana Lizarazo.