In this paper, a new effect of pitch proximity is reported. Subjects were presented with patterns consisting of octave-related complexes. Each pattern was composed of four tones, which constituted two simultaneous melodic lines, one of which ascended by a semitone while the other descended by a semitone. The subjects judged whether the line that was higher in pitch ascended or descended, and from these judgments it was inferred which line was heard as higher and which as lower. It was found that the patterns were perceptually organized so that the simultaneous tones formed proximal relationships. The findings provide evidence that, just as successions of tones tend to be organized perceptually in accordance with pitch proximity, so simultaneous tones tend to be organized in accordance with this principle also.