Pool flames of heptane, kerosene, and crude oil in a 2.7m square tank were measured by thermography, storing thermal images as TV color images with 25,600 data points every 0.1 second. These apparent temperature images can be converted to irradiance by simple approximations. A series of data recorded continuously at 0.1 second intervals (70 images for one fuel) were analyzed statistically to obtain the distribution of mean radiance, standard deviation and coefficient of variation in the thermography image. The contours of mean radiance, standard deviation and coefficient of variation related to radiance were made, and the flame structure of pool flames is considered from a radiation point of view. The height of maximum radiance from the tank top is obtained from the contours of the mean radiance. Mean paths of formation, growth, and dissipation of vortices are obtained by the contours of the standard deviation on radiance. The stable flame regions and the lower part of plume regions are also obtained by using the contours of the coefficient of variation based on radiance. Flame structures obtained by processing thermographic data are also compared with previous work by McCaffrey who defined flame, intermittent, and plume regions by the temperature and velocity distribution along the center line of flames. By this comparison, statistical analysis using thermographic data is also useful to assess the flame structure of large pool fire flames. Finally, the radiative characteristics of the continuous flame, intermittent, and plume regions, are established