For the last 100 years, diagnosis of malaria has been based on examination of Giemsa-stained thick and thin blood films under the microscope. This is a time-consuming procedure which often fails to correctly diagnose the infecting species--especially when carried out by inexperienced technicians or when blood levels of parasite are low. Rapid Diagnostic Tests (RDTs) for antigen detection can distinguish between Plasmodium falciparum and Plasmodium vivax but cannot identify the species present in mixed infections. In the case reported here we used multiplex PCR to investigate suspected mixed infection in a pregnant woman from Nigeria. The results suggest that the method used is highly specific and can be very sensitive and that it has several advantages with respect to microscopy and RTDs.