Since 1881 when Englemann reported aerotaxis in bacteria, an understanding of the molecular nature of the signal transduction remains a daring goal for microbiologists. This short review discusses known facts and recent advances in the field including the discovery of the flavoprotein receptor which drives Escherichia coli towards oxygen. Possible mechanisms of oxygen sensing in various bacterial species are considered in connection with the existing, often fragmental, data on phototaxis, redox taxis and taxis repellent effect of the reactive oxygen species (ROS).