A method for establishing temperature and humidity profiles inside a fluidized bed during particulate coating has been developed. The process involves direct measurement of the variables at selected points, generating extra points in between the measured points and then processing them to obtain the profiles. A computer program is used to superimpose the profiles and contours, thus showing how different parts of the bed are involved in the coating process. The analysis of the profiles together with the characteristics of the measured values has led to the delineation of the bed into different zones. Different colours or greys can be used to represent different intensities in assessing the effect of different variables on the process and thus provide a valuable tool for the design and optimization of fluidized bed processes.