Abstract: A target for measurement of critical dimension bias on a substrate formed by a lithographic process comprises six contrasting arrays of elements on first and second layers of the substrate. Each of the arrays has a plurality of spaced parallel elements contrasting with the substrate. Ends of the contrasting elements are aligned along parallel lines forming opposite array edges, with the length of the contrasting elements comprising the array width. The array edges are measurable by microscopy without resolution of individual elements of the array. The arrays are spaced apart in the X-direction, with three on a first layer of the substrate and three on a second layer of the substrate. The first, second and third contrasting arrays of elements on the first layer of the substrate are interposed between at least two of the fourth, fifth and sixth contrasting arrays of elements on the second layer of the substrate.