The stage specificity and localization of 12 Plasmodium falciparum antigens were determined by immunofluorescence using acetone-fixed parasites reacted with mono-specific antibodies against cloned antigens. Antibodies were prepared by immunization of rabbits with recombinant proteins or by affinity purification of human plasma against cloned antigen adsorbents. Most of the antigens occurred predominantly in mature sexual parasites, two were abundant in ring stages and three were absent in rings. Four of the 12 antigens were detected in asexual stages but not in gametocytes. Grouping of antigens by localization within blood stages was difficult because of the complexity of fluorescence patterns observed. With some antibodies, fluorescence was apparently distributed evenly over the parasites, but in other cases label was concentrated within discrete compartments or organelles. Extraparasitic intraerythrocytic fluorescence was also observed.