[en] A laboratory test of the inverse square law of gravity has been conducted. The almost null field inside a long precisely machined tube was probed by a test mass suspended from a torsion balance. In terms of a distance-dependent gravitational constant G(r), the experiment is sensitive to variations in G(r) over the distance range of approximately 2 to 5 cm. If G(r) = G0 [1 + epsilon In r(cm)], epsilon is found to be (1 +- 7) x 10-5, in support of the inverse square law