Remarkably high apparent peak efficiencies (10(6)-10(9) theoretical plates per meter) in capillary electrophoresis (CE) could be achieved in the separation of two different kinds of bacteria and Baker's yeast using poly(ethylene oxide) as a necessary buffer additive. In these applications no deliberate stacking procedure was implemented. Seemingly, the investigated organisms in this study behave differently than molecules under an applied electric field. For molecules, these extremely high efficiencies are very unusual. Using a 488 nm argon-ion laser coupled to a charge-coupled device (CCD) camera it was possible to monitor the migration behavior of stained microorganisms over a length of 10 cm. This part simulates the very beginning of the CE run. In specific cases 60-70% of the monitored detection window could be filled with analyte without significant loss in peak efficiency. For a mixture of two different microorganisms the occurring separation process could be followed in detail. The effect of buffer concentration, polymer type, polymer molecular weight, polymer concentration, pH, and the effect of injection time was investigated. The expansion of fast and reproducible CE separations to other unicellular organisms may become a powerful tool in microbiological science and technology.