The isolation yield and number of Chlamydia trachomatis inclusions was compared using DEAE-dextran pretreated HeLa cells cultured in four different media: Eagle's minimal essential medium (EMEM) with and without cycloheximide and Dulbecco's modification of EMEM (DMEM) with and without cycloheximide. Using DMEM without cycloheximide the number of inclusions was significantly higher than using EMEM without cycloheximide. In addition, the size of the inclusions was greatly enhanced. Use of DMEM or EMEM with cycloheximide yielded results comparable to those obtained with DMEM without cycloheximide.