The invention relates to a gas bag for vehicles, having a flat, two-dimensional shape when being in an uninflated, vented condition and a three-dimensional shape in an inflated condition, the gas bag having a main piece with opposite end portions, each of the end portions having an end contour, and two minor pieces which each have a connecting portion with a contour with corresponds to the end contour of the main piece, and which each have a filling portion, the two filling portions having similar shapes and similar dimensions. The invention also relates to a method of sewing this gas bag.