A mutation in the Escherichia coli gene encoding the stationary phase‐inducible sigma factor (σ^s, RpoS) not only abolishes transcription of some genes in stationary phase, but also causes superinduction of other stationary phase‐induced genes. We have examined this phenomenon of repression by σ^s using as a model system the divergently transcribed stationary phase‐inducible genes, uspA and uspB. uspA is transcribed by σ⁷⁰‐programmed RNA polymerase and is superinduced in an rpoS mutant, while uspB induction is σ^s dependent. The data suggest that the superinduction of uspA is caused by an increased amount of σ⁷⁰ bound to RNA polymerase in the absence of the competing σ^s. Increasing the ability of σ⁷⁰ to compete against σ^s by overproducing σ⁷⁰ mimics the effect of an rpoS mutation by causing superinduction of σ⁷⁰‐dependent stationary phase‐inducible genes (uspA and fadD), silencing of σ^s‐dependent genes (uspB, bolAp1 and fadL) and inhibiting the development of σ^s‐dependent phenotypes, such as hydrogen peroxide resistance in stationary phase. In addition, overproduction of σ^s markedly reduced stationary phase expression of a σ⁷⁰‐dependent promoter. Thus, we conclude that sigma factors compete for a limiting amount of RNA polymerase during stationary phase. The implications of this competition in the passive control of promoter activity is discussed.