The paper presents materials on age-related morphology of the bone marrow of Guinea fowl of the Volga white breed. The bone marrow is placed in the cancellous cells, and in the postembryonic period its absolute mass increases, and the relative weight, on the contrary, decreases. The highest content of the bone marrow in the skeleton of a Guinea fowl is observed in the period from the 1-st till the 60-th days of life. The volume of the bone marrow in the male Guinea fowl is higher than in the female Guinea fowl on 1,7+0,15%. The main mass of the bone marrow in a newborn Guinea fowl is placed in the peripheral skeleton, and more than 45% in the humeral, femoral and tibial bones. As for the axial skeleton, most of it is concentrated in the iliac bone and the lower jaw. Further the number of a bone marrow sharply increases and reaches a maximum to the 60-th day of life, consisting of 37.10+of 1.51% from the total content of the skeleton of a Guinea fowl. Then this figure stabilizes and to the 90-th day of life it consists of 34,90+1,89%. From the 180-th day of life the amount of a bone marrow in the skeleton begins to decrease and to the 365-th day it consists of only 23,10+of 1.11%. Microscopy of smears of a bone marrow finds an individual fat cells in it from the 60-th day of life. By the time of a puberty is observed a gradual replacement of a red marrow to the yellow and to 180-th day it is only 15,75+1,28%. By the 365-th of life a bone marrow is mostly yellow with a single foci of hematopoiesis in its structure, up to 8,31+1,56%.