The state of the system «primary kidney of a Syrian hamster» at the stages of embryonic development was studied. The informational characteristic of the complexity and organization of the morphological system «primary kidney» was carried out by calculating the indicators: informational maximum entropy (Нmax): (Нmax) = Iog2n, where n is the number of classes, informational entropy (Н), as a measure of information uncertainty according to Shannon’s formula Н = -∑Рi Log2Pi, where Р – volume fraction of tissue components of the primary kidney; information organization of the system (S): relative entropy (h), coeffi cient of relative organization of the system (or coeffi cient of redundancy) (R): R = (Hmax-H) / Hmax 100%. Based on the studies carried out, it was found that the entropy of the «primary kidney» system in embryos increases by the end of the 1st stage of the organ’s life cycle to 1.07 bit, at the 2nd stage it decreases to 0.80 bit, which is associated with an increase in the proportion of mesenchyme and its predominance. over other structural components. The redundancy ratio increases in the middle of stage 1, then decreases towards the beginning of stage 2, then from the middle of stage 2, the redundancy ratio increases until the end of stage 3, which is associated with an increase in the stability of the system. The relative entropy during the observation period decreases from 52.54% at the beginning of stage 1 of the organ’s life cycle to 39.93% at stage 3.