A report was made of 4 cases of chloroquine resistant Plasmodium falciparum infections. The infections, detected in Jakarta, were imported from Kotabumi, Tanjung Karang, the Island of Pidada in the Lampung Province and from Pangkalpinang on the Island Bangka in the Province of South Sumatra. Treatment with courses of 1500 mg chloroquine base and with increased dosages up to 2250 mg base failed to cure the patients. The chloroquine sensitivity test in vitro was carried out in 3 patients, which showed that the Plasmodium falciparum strains were resistant to chloroquine at the R I level. The strains appeared to be similar to the Malaya Camp strain. In vivo observations revealed that the parasites were resistant at the R I level with a delayed recrudescence. The chloroquine resistant falciparum malaria cases, acquired in South Sumatra, may therefore be regarded as the first reported cases from a focus outside the already known two foci in Indonesia, namely East Kalimantan and Irian Jaya. It may be expected that chloroquine resistant Plasmodium falciparum will be encountered in other parts of Indonesia in the near future. The use of a combination of sulfadoxine and pyrimethamine should not be recommended in Indonesia because chloroquine is still considered the drug of choice against all malaria infections in Indonesia.