Abstract: Optical data storage members in which the guard bands present between data-carrying tracks of conventional data storage members are used to carry information recorded in a manner which avoids the danger of cross-talk between adjacent tracks. One preferred arrangement consists of an optical data storage member comprising an optically recordable surface having a plurality of tracks in which information may be recorded in analogue or digital form, the tracks being of a first type in which the material constituting the track is sensitive to radiation of a first predetermined characteristic and a second type in which the material thereof is sensitive to radiation of a second predetermined characteristic, wherein tracks of the first type alternate across the surface of the second type. The tracks may be constituted by a surface region (1,2,3,4,5) carrying a plurality of closely spaced grooves (11,12,13,14,15), the grooves of one track being orthogonally directed with respect to those of its adjacent tracks.