A number of hydrocarbon flame bands have been photographed in high orders of diffraction of a 3.4-m Ebert spectrograph, with an achieved resolving power of about 100,000. The spectrum contains both sharp and diffuse bands, and there are two distinct types of band envelope. Strong evidence is presented that the lower state of the hydrocarbon flame bands is the [graphic omitted], 2A′ ground state of the HCO radical, and that the A and B bands form two separate band systems. The origins are assigned as : [graphic omitted], 2A′ state, T00= 38691 cm–1, [graphic omitted] state, T00= 41270 cm–1. Partial rotational analyses of three bands in the A1 progression show that these are type a bands, and lead to the following structure for HCO in the [graphic omitted], 2A′ state : rCH= 1.16 Å(assumed), rCO= 1.36 ± 0.02 Å, HCO = 111 ± 4°.