a simplified lead citrate stain for use in electron microscopy is described. the traditional lead citrate stain, known as reynolds' stain, requires several steps and time for preparation. this new method uses a commercially available lead citrate solution to eliminate these steps. the stain is prepared by mixing 0.01 to 0.04 grams of lead citrate with 10 ml of distilled water and 0.1 ml of 10n sodium hydroxide. the resulting solution provides contrast and delicacy equal to reynolds' stain. the preparation takes less than 5 minutes. to prevent lead carbonate precipitation, the solution should be made with concentrated sodium hydroxide or pellets and kept sealed from atmospheric carbon dioxide. sections are stained by placing them in the solution on clean surfaces. staining times vary depending on the tissue type. after staining, sections are washed and air-dried before examination. short staining times (1 minute or less) are generally sufficient, as longer times may cause over-staining. double staining with uranyl acetate followed by lead citrate requires only a few seconds in each solution. if large particulates appear, the stain should be discarded. if fine dots appear, the lead citrate concentration may be too high. if dots appear in unstained sections, they may be due to non-specific osmium tetroxide precipitation. unexplained staining failures should be addressed by discarding the stain and making a fresh solution. if failures continue, a new source of sodium hydroxide and purer water should be sought. the stain has been successfully used in the laboratory for over a year on various tissues.a simplified lead citrate stain for use in electron microscopy is described. the traditional lead citrate stain, known as reynolds' stain, requires several steps and time for preparation. this new method uses a commercially available lead citrate solution to eliminate these steps. the stain is prepared by mixing 0.01 to 0.04 grams of lead citrate with 10 ml of distilled water and 0.1 ml of 10n sodium hydroxide. the resulting solution provides contrast and delicacy equal to reynolds' stain. the preparation takes less than 5 minutes. to prevent lead carbonate precipitation, the solution should be made with concentrated sodium hydroxide or pellets and kept sealed from atmospheric carbon dioxide. sections are stained by placing them in the solution on clean surfaces. staining times vary depending on the tissue type. after staining, sections are washed and air-dried before examination. short staining times (1 minute or less) are generally sufficient, as longer times may cause over-staining. double staining with uranyl acetate followed by lead citrate requires only a few seconds in each solution. if large particulates appear, the stain should be discarded. if fine dots appear, the lead citrate concentration may be too high. if dots appear in unstained sections, they may be due to non-specific osmium tetroxide precipitation. unexplained staining failures should be addressed by discarding the stain and making a fresh solution. if failures continue, a new source of sodium hydroxide and purer water should be sought. the stain has been successfully used in the laboratory for over a year on various tissues.