An experimental and theoretical study of the structure and radiation properties of round, turbulent, luminous ethylene/air diffusion flames is described. Measurements included mean and fluctuating velocities, mean concentrations of major gas species, soot volume fractions, monochromatic absorption (632.8 nm), spectral emission (1000–5500 nm), and total radiative heat flux distributions. Flame structure was predicted using a Favre-averaged k-∈-g turbulence model and the laminar flamelet approximation. Spectral radiation intensities were predicted using a narrow-band model—both ignoring (using mean properties) and considering (using a stochastic method) turbulence/radiation interactions. Total radiative heat fluxes were found by summing spectral intensities over wavelength and paths through the flame. The comparison between predicted and measured flame structure was reasonably good. Differences between mean-property and stochastic radiation emission predictions were significant (50–300 percent) suggesting strong turbulence/radiation interactions in luminous flames. However, both radiation analyses represented trends due to changes in position and burner flow rate reasonably well. This suggests that soot volume fractions may approximate universal functions of mixture fraction in turbulent flames, even though this correspondence is only crudely observed in laminar flames due to hydrodynamic complications of soot particle motion.