Venus Williams booked her place in the second round of the Internazionali BNL d'Italia on Monday, 17 years after first winning the tournament.
Returning to action after a one-month lay-off, the 1999 Rome champion secured a 6-4, 6-3 victory over fellow American CoCo Vandeweghe.
Surprisingly, it was the first meeting between the two Fed Cup team-mates.
"I have hit with her a little bit at Fed Cup but not really sure what to expect," Williams said after the match. "I imagine that on the clay I have a little bit more advantage, just having played more matches on clay. I think that helped a lot."
After an evenly contested opening half hour, Williams broke for a 5-3 lead, but then failed to serve out in her next game as Vandeweghe immediately regained the lost advantage.
It proved to be only a temporary comeback, however, as Williams manufactured another break in the next game to go one set up.
An early break in the second set, gave Williams a 3-1 lead and she did not give her opponent a sniff after that, wrapping up the match in 89 minutes.
Williams struck 13 winners and 16 unforced errors to Vandeweghe's 20 and 27.
— WTA (@WTA) May 9, 2016
Also advancing was 10th seed Lucie Safarova, who was a 6-3, 6-2 winner over former French Open champion Francesca Schiavone on the Italian's home court.
The Czech had too much firepower for her opponent on the day, hitting 17 winners to Schiavone's six.
"Francesca is a great player," she said. "She has a lot of spin and runs well, so it's never easy to play her. But I was playing really great today, aggressive, and took time away from her, so I'm happy I won."
A trio of seeds were eliminated on the day, as Monica Puig knocked out 15th seed Elina Svitolina 6-1, 4-6, 6-1, while Heather Watson accounted for another local favourite, 14th seed Sara Errani, 6-4, 3-6, 6-0.
Karolina Pliskova, the 16th seed, was also bundled out, going down 6-4, 6-4 to Daria Kasatkina.
Others to move on to the second round on the day included Teliana Pereira, Ekaterina Makarova, Madison Keys and Barbora Strycova.