A rapid method for the preparation of bacterial DNA for pulsed-field gel electrophoresis was developed for Gram-positive and Gram-negative bacteria. This method mns accomplished by reducing the time for the cell lysis reaction, restriction endonuclease digestion, and electrophoresis to 1, 1.5, and 18 h, respectively. The whole procedure from the initial bacterial culture plate to the final analysis of restriction fragments can be completed within 24 h. This rapid method was successfully achieved for Staphylococcus aureus, Enterococcus faecalis, Neisseria gonorrhoeae, Salmonella typhimurium, Serratia marcescens, and Stenotrophomonas maltophilia. (C) 1998 Elsevier Science Inc.