A new approach to determining the solar galactocentric distance, R0, from the geometry of spiral-arm segments is proposed. Geometric aspects of the problem are analyzed and a simpli¯ed three-point method for estimating R0 from objects in a spiral segment is developed in order to test the proposed approach. An estimate of R₀ = 8:44 ± 0:45 kpc is obtained by applying the method to masers with measured trigonometric parallaxes, and statistical prop-erties of the R0 estimation from spiral segments are analyzed.