Antixenosistests are commonly conducted in green bug, Schizaphis graminum (Rondani), plant resistance research; however, the variability in these tests is often high. Our objectives were to determine whether directional responses occur in traditional greenhouse antixenosis tests, and to develop a design that would result in less variability. We evaluated three kinds of antixenosis tests: (1) the standard test consisting of barley, Hordeum vulgare L., with test plants planted at random in a circular pattern near the edge of a greenhouse pot (replication) and analyzed as a randomized complete block design (RCBD); (2) a completely randomized design (CRD) in greenhouse flats; and (3) a completely randomized design with a central composite arrangement (CRD-CCA), also in flats. Apterous biotype E green bug adults were used in all tests. Directional tests indicated that more green bugs selected plants toward the direction of the sun, which would cause high variability in the standard antixenosis test. After comparing the error mean squares and coefficients of variation, and considering the impracticality of conducting a CRD-CCA with more that five or six test entries, we concluded that the CRD is the best of the three designs for green bug antixenosis tests in a greenhouse.