Benign paroxysmal positioning vertigo (BPPV) and nystagmus (BPPN) is the commonest type of rotational vertigo, but its origin is not fully understood. In this study we used search coils to measure 3-D eye position in 5 patients with BPPN. We present for the first time a complete three-dimensional description of the eye movements induced in BPPN. By calculating the eye movement direction in head co-ordinates we are able to relate the elicited nystagmus very precisely to a particular canal and thereby localize the lesion.