Although it is known that magnetic recording system performance can be improved by reducing the separation between the head and media, few detailed measurements of the spacing dependence of recording performance (rolloff curves, isolated pulse heights and widths, etc.) have been made. Most measurements reported to date are at low linear velocities using flexible media and deposited oxide layers on the head1 or carbon overcoats of various thicknesses on the flexible disk2 to maintain a given spacing. This paper presents the results of measurements made with a novel device which positions the head at arbitrary (and continuously variable) heights above a rigid magnetic disk operating at a high and constant linear velocity. Separate read and write spacing loss measurements were made using a 3380‐type thin‐film head and metal film disk at a number of spacings ranging from 0.075 μm (3 μin.) to 0.5 μm (20 μin.). The results are analyzed using head sensitivity functions computed by the boundary element method. Good agreement between theory and data is found at linear densities in excess of 2500 fc/mm. The advantages of magnetic recording at small head/disk spacing are discussed. © 1988, American Institute of Physics. All rights reserved.