A procedure is described for making diatom microscopy slides from large numbers of sediment samples, simultaneously. The method uses small sediment samples, small test tubes, small amounts of hydrogen peroxide, no decantings, no centrifuging, and it requires no washing-up of glassware. It is, therefore, fast, cheap, gentle to the diatoms and needs little fume cupboard space. © 1990 Kluwer Academic Publishers.