Defending champion Martina Navratilova and third-seeded Pam Shriver gained the third round of the Australian Open championships at Kooyong today.

Navratilova routed Mary Lou Piatek, 6-2, 6-1, for her 72nd consecutive victory. Shriver eliminated Corinne Vanier by the same score.

If Navratilova wins this tournament, she would set a record of seven consecutive Grand Slam tournament victories. It would also be her 100th tournament victory.

Navratilova will face Kathy Rinaldi in the third round. Shriver, still bothered by a shoulder injury, will face Elizabeth Minter.

In a Thursday night match, No. 2 seed Chris Evert Lloyd defeated Miriam Schropp, 6-1, 6-0, keeping her on schedule for an anticipated meeting in the final with Navratilova. It was Evert's 999th tournament victory.

In men's matches Friday, No. 3 seed Joakim Nystrom beat Colin Dowdeswell, 6-4, 6-2, 6-4; No. 9 Kevin Curren eliminated Wally Masur, 6-4, 6-4, 6-4, and Scott Davis ended the tournament for Chris Lewis, 6-4, 6-2, 6-0.

Lewis, beaten by John McEnroe in the 1983 Wimbledon final, has won only 15 matches in 20 tournaments this year.

On Thursday, defending men's champion Mats Wilander, No. 4 in the world, had a tough time with No. 174 David Mustard before beating him, 1-6, 6-3, 7-5, 6-3.

Two-time men's champion Johan Kriek opened the center-court program Thursday with a 6-3, 6-3, 7-6 victory over Brad Drewett.