This invention relates to a postural system which can advantageously be used by both properly walking persons and non-ambulant and partially ambulant persons, and in the latter case is suitable for use with or incorporation with medical support devices for mobility, medical devices for rehabilitation and social or domestic life and the like: this system may also be advantageously used with or incorporated with transport means. The postural system according to the invention provides a supporting structure comprising a flat base plate (10) and a plurality of modular blocks (20a-20f, 30a-30d, 40a-40f, 50a-50e, 80a-80b) intended to support various segments of the user's body (legs, pelvis, spine and so on). The number, shape, size and orientation of the said modular blocks can be suitably selected to obtain a perfect fit for the user's shape (whether male or female) and encourage perfect housing of the body and a correct weight distribution over the entire surface of the seat.