The establishment of new strains of Plasmodium falciparum in continuous culture is described. One line (FCR-2), isolated from an individual who had traveled extensively through South America, was passed initially through Aotus trivirgatus monkeys and then cultured into human erythrocytes using the flow-vial technique. A strain of P. falciparum FMG), shipped by air freight on wet ice from The Gambia, was cultured directly from a human infection into continuous culture using the Petri dish-candle jar technique, giving line FCR-3. Two other strains (6252 and FSG) were hand carried by a commercial flight on wet ice from the Gambia and were initiated into culture at the same time using the same media, sera, and erythrocytes. After 6 wk in vitro the 6252 strain became adapted as line FCR-4, whereas FSG had died out. Normal-looking gametocytes were seen in all four strains reported here. Notwithstanding their normal appearance they would not exflagellate in vitro, nor were they infective to Anopheles stephensi mosquitoes via membrane feeding. Production of new gametocytes continued for 6 mo, then gradually stopped.