ABSTRACT. The effect of low incubation temperature on synchronized cultures of Plasmodium falciparum was studied. Young trophozoites that were maintained at 28°C matured slowly and invaded poorly. Growth seemed to arrest when parasites reached a maturation equivalent to 30 h, although they reestablished their growth normally when returned to 37°C. On the other hand, 36‐h synchronized parasites that were transferred to 28°C completed their cell cycle with a 12‐16 h delay, but without changes in the parasite as seen by light microscopy and without a diminution in the efficiency of the invasion or in the incorporation of 35 S‐methionine. These results might be useful for obtaining parasites at defined stages of development at the desired time.