Last year Ms Heywood and Ms Agnew, along with Maryanne Rogers-Benton, Carol Thorpe and Sylvia Wilmshurst won gold medals in the Adelaide tournament in the age group 55 to 64 section 2 of three sections.
"This year we have been promoted to Section 1 of 55 to 59 age group which will be a lot tougher," Ms Agnew said.
There are five venues for this year's competition - Miami Tennis Club, Gold Coast Seniors, KDV Sports, Tweed Heads and Fairways - with 116 teams competing from ages 35 plus to 75 plus in both men's and women's divisions.
Teams have entered from Japan, Europe, New Zealand and all the states of Australia. The court surfaces are synthetic grass and clay.
There are three women's teams representing New Zealand in the 55 plus , 60 plus and 75 plus sections.
The teams are:
Womens 55 plus - Raewyn Heywood, Janet Agnew, Leona Davis-Kay, Carol Thorpe, Deanna Pohatu.
Womens 60 plus - Trish Craven, Wendy Wrigley, Marietta Duffy-Burgess, Ann Volmuller.
Womens 75 plus - Tup Cox, Bev Evans, Janice Larmer, Jillian Roberts, Gloria Wilmot.