The use of preheated air as the oxidizer is a key technology in regenerative combustion. Results have been obtained on the homogeneity and stability of normal and highly preheated air (1000°C) temperature flames using methane and propane as the fuel. The volume fraction of oxygen in air was varied from 10% to 20%. A spectral video camera was used to obtain spectrally (band pass=15 nm) and time-resolved (128 frames with a gate time of 5 ms) images of OH, CH, and C 2 emissions from the flames. These images were further processed on a PC using an image processing software. Fast Fourier transform (FFT) applied to the frequency-domain images provided information on the spatial distribution of flame flicker. Spatial intensity distribution was obtained via integration over the 128 frames. Information on the spatial distribution of vibrational temperatures has also been obtained by comparing two different C 2 bands. The results showed significant differences in the spatial distributions of OH, CH, and C 2 emission as well as the vibrational temperatures from room-temperature and highly preheated air flames, under identical operational conditions. Flames with preheated air were much more homogeneous and stable as compared to the room-temperature air.