Two experiments considered the effects of introducing an extreme stimulus (anchor) upon the differential perception of tonal stimuli. In the first experiment, in which Ss rated series stimuli from 1,000 to 2,000 Hz or from 2,000 to 3,000 Hz, the presence of a 750-Hz anchor apparently disrupted discrimination. A second experiment involved testing for a difference threshold (method of limits) in which the standard was a tone of 1,500 Hz. The uncertainty interval (Iu) was larger when the interval between paired stimulus presentations was filled with a 750-Hz tone, again suggesting that discrimination is impaired by the introduction of a low-frequency anchor. Results are discussed in terms of theories relating range extent and discriminability. Anchor effects (AE), for this study, are measured in terms of the modification of judgments made about a series of stimuli as the result of the presence of a stimulus value which falls outside the series. One conjecture about such effects is that they are limited by the distance of the anchor from the series stimuli. A further conjecture is that such limits may define relevance between an anchor value and a particular set of stimuli, possibly leading to description of stimulus dimensions in terms of a minimal number of relevant subsets (e.g., Adamson, 1967; Bevan & Pritchard, 1963; Sarris, 1969). This study began with an attempt to define AE limits for a portion of the auditory frequency dimension, itself chosen as possibly anomalous when compared to other quantitative dimensions (see Attneave & Olsen, 1 9 71 ). The singular findings of Experiment 1, however, prompted a change in direction and necessitated running a second experiment, in an attempt to ascertain whether the findings were related to basic properties of the perception of pitch. EXPERIMENT1