Alexander Rossi and Ma Qing Hua have been confirmed as reserve drivers for Caterham.
Rossi, who took part in practice during last year's Spanish Grand Prix, will drive in a number of practice sessions in 2013.
Ma joined HRT in 2012 and took part in four practice sessions. He will drive for Caterham during practice for the Chinese Grand Prix.
"2013 will be my third season with the Caterham family and I’ve built solid relationships within the whole team," said American driver Rossi.
"My goals from the Friday practice sessions that I will drive this season is to fulfill the team’s runplan for each session, work closely with everyone and learn as much as possible, always being ready for the next opportunity. As Caterham F1 Team’s Reserve Driver I will attend all F1 events, allowing me to integrate fully within in the team technically, commercially and from a sporting perspective in F1, best preparing me for the next step."
Ma will also race in GP2 for Caterham Racing.
"I am very excited about joining the Caterham family and would like to thank everyone at Caterham F1 Team and Caterham Racing for giving me the chance to race in GP2 and to extend my F1 experience," said the Chinese racer.
"Both teams have everything they need to keep growing in the right direction and I am looking forward to playing an important role in helping them achieve what they’ve set out to this year. I know the fans at home will be really excited to see me race in GP2 and with the F1 work I also have ahead of me, China can be proud that it continues to have a driver involved in motor racing at the very highest level."