A method is described for the fully automated reading of Plasmodium falciparum drug susceptibility tests. Cultured material was fixed and could be stored for ≥6 months until analysis. The parasites were stained for DNA with the fluorescent dye Hoechst 33258 and analyzed by flow cytometry. The procedure was done in 96-well microtiter plates, after which the material was directed through the sensing region in the flow cytometer. The data resulting from the analysis were stored by microcomputer and processed by a program developed for this purpose. Using this method, a number of different parameters describing the growth in culture can be assessed.