Growth of Escherichia coli and chemical changes in the medium were very similar in highly baffled flasks and in a 50-liter fermentor run under the same oxygen-supply conditions, based on sulfite-oxidation rates. Flasks with stainless-steel baffles (Biotech) gave growth patterns and rates of glucose and NH(4)-N utilization almost identical to those of the fermentor; results with Bellco 598 flasks (with 6 to 7 mm deep indentations) were quite similar. Unbaffled and Bellco 600 flasks (3 to 4 mm indentations) were similar to the fermentor at very high and very low oxygen-transfer rates, but gave much less growth than the fermentor at intermediate levels. Maximal oxygen-uptake rates occurred in the fermentor at the end of the logarithmic-growth phase when growth was 40 to 75% of maximum. In the fermentor, both sulfite-oxidation rates and rates of oxygen uptake correlated reasonably well with the total amount of growth produced.