Laura Robson and James Ward won their opening qualifying matches at the Sony Ericsson Open in Miami but there was disappointment for fellow Britons Anne Keothavong, Naomi Broady and Dan Evans.
Robson made light of a gap of 37 ranking places to beat Russia's world number 83 Alexandra Panova 6-3 7-6 (7/3), while Ward was an impressive 6-3 6-3 winner against Kazakhstan's Andrey Golubev, a player 24 places ahead of him in the rankings at number 138.
However Keothavong, despite being the second seed in women's qualifying, was knocked out 6-4 6-3 by Japan's Misaki Doi, Broady was thrashed 6-3 6-0 by qualifying top seed Kateryna Bondarenko of Ukraine, and Evans lost 7-6 (7/4) 6-0 to Germany's Bjorn Phau.
Robson and Ward must win another round to reach the first-round proper of the lucrative event, which runs through to April 1.
Britain's Andy Murray and Elena Baltacha are in the main draw by right, and Heather Watson has been granted a wild card.
Baltacha will play Serena Williams in the second round, should the Scot beat China's Zhang Shuai in her first match.