Background: various variants and developmental anomalies of the lumbosacral spine that cause the vertebralsacral vertebrae are often identified during diagnosis as an accidental finding due to the availability and widespread use of modern imaging methods. Material and methods: the material for the study was 24 X-ray images of the lumbosacral spine of persons of both sexes aged from 27 to 69 years, performed in frontal and lateral projections. X-ray anatomical analysis was performed by the method of fluoroscopic examination, the results obtained were described according to the classification of transitional vertebrae according to A.E. Casellvi. Results: eight radiographs revealed a shadow of an additional vertebra in the lumbar spine, the height of which was reduced in 92.4% of cases, and the spinous process was shortened in 87.6% of cases. On 16 images, onesided lumbalization was determined, a one-sided visible gap in the upper sacrum was revealed. Conclusions: in the course of the study, an X-ray anatomical analysis of the transitional lumbo-sacral vertebra with determination of the type according to the Casellvi’s classification of transitional vertebrae. In 33.4% of cases, type I with complete lumbalization was detected, in 66.6% of cases, incomplete lumbalization was revealed, characterized by various anatomical variants, classified in types II and III.