Disclosed is a substrate comprising a combined target for measurement of overlay and focus. The target comprises: a first layer comprising a first periodic structure; and a second layer comprising a second periodic structure overlaying the first periodic structure. The target has structural asymmetry which comprises a structural asymmetry component resultant from unintentional mismatch between the first periodic structure and the second periodic structure, a structural asymmetry component resultant from an intentional positional offset between the first periodic structure and the second periodic structure and a focus dependent structural asymmetry component which is dependent upon a focus setting during exposure of said combined target on said substrate. Also disclosed is a method for forming such a target, and associated lithographic and metrology apparatuses.