The assessment of spray uniformity is an important step in the fabrication of powders in spray drying processes. The most common approach is based on the relative span, but it has its limitations. And, in some cases, it is shown to be less reliable than initially thought. The underlying reason is that it considers certain characteristic parameters extracted from the probability distribution, but not the distribution itself. This is why, based on experimental evidence obtained in ultrasonic sprays, a more reliable approach is suggested as spray uniformity index based on information theory through the normalized Shannon information entropy.