We investigated the perceived frequency elicited by two vibrating probes on the skin. Participants (n = 11) compared two probes vibrating in counter-phase (25 Hz), with comparison stimuli of in-phase vibration (18-54 Hz). They indicated which had the higher perceived frequency. Skin sites on the palm (glabrous) and arm (hairy) were tested with a range of probe separations (1-16 cm) and amplitudes (10-120 mu m). Perceived frequency increased with decreasing separation of the probes (F-1,F-10 = 182.8, p amp;lt; 0.001). The two skin sites did not significantly differ (F-1,F-10 = 3.6, p = 0.087). Perceived frequency was only minimally affected by amplitude changes between 40 and 120 mu m (F-2,F-20 = 6.4, p = 0.007, eta(2)(G) = 0.06). Both phase and spatial separation strongly influence vibrotactile interaction between two skin locations in a manner largely independent of changes in amplitude, and of skin type.