A technique is presented for evaluating aperture synthesis arrays of radio telescopes. Results can be either quantitative or graphical. A numerical quality index specifies the weighted average uniformity with which an aperture can be synthesized. Application to very long baseline interferometry is illustrated by analysis of arrays of existing antennas in the United States with and without a new telescope in the Midwest (prairie states). The optimum location for a new telescope is within 87.0°–89.2° west longitude and 38.3°–39.5° north latitude.