Mixed malaria infections are common. In Thailand, despite low levels of malaria transmission, one-third of patients with acute P. falciparum infection are co-infected with P. vivax, and 8% of patients with acute vivax malaria have simultaneous P. falciparum infection. Mixed infections are underestimated by routine microscopy. Cryptic P. falciparum infections can be revealed in approximately 75% of cases by the RDTs based on the histidine-rich protein 2 (HRP2) antigen, but such antigen tests are much less useful (because of their lower sensitivity) in detecting cryptic vivax malaria. ACTs are effective against all malaria species and are the treatment of choice. Radical treatment with primaquine should be given to patients with confirmed P. vivax and P. ovale infections except in high transmission settings where the risk of re-infection is high.