This experiment was designed to determine whether a previously established flicker (or fusion) threshold in one eye could be altered by manipulating the light-pulse rate in the other eye. Using an instrument that allowed separate pulse presentations for each eye, both the flicker and fusion thresholds were obtained for one eye (called the target eye). Then the pulse rate was varied in the other eye (called the manipulated eye), in an effort to shift the threshold in the target eye either from flicker to fusion or from fusion to flicker. Although a variety of pulse rates were presented in the manipulated eye near the thresholds of the target eye, there was no significant evidence that the threshold (either fusion or flicker) values were altered. Thus, our view that a flicker-fusion threshold interdependency exists between the two eyes was not supported.