A disposable, single-use, generally elongate diaper having substantially planar sections at each end and intermediate these planar ends a substantially non-planar section comprising the crotch section. The crotch section is narrower than at least one of the ends and is longitudinally constricted by elastically extendible means secured to each of the edges of the crotch section in a manner which produces a plurality of gross transverse rugosities across the width of the crotch section of the diaper when the elastic means is in non-extended condition. The width dimension of the crotch is preferably within a predetermined percentage range of the combined width of the planar waist sections. The length dimension of the narrower crotch section is preferably a specified percentage of the full unconstricted length of the diaper. A further improvement is obtained if the geometry of the side edges between the wide waist section and the narrower crotch section is defined by a concave arc.