Many studies have indicated that a component of the distal nephron inн teracts significantly with the glomerular vascular elements of each neн phrovascular unit. The structural link that supports this hypothesis is the intimate morphological association between the macula densa cells of the distal tubule and the glomerular structures (13, 56). The distal tubular feedback hypothesis (also referred to as tubulo-glomerular feedback) proн poses that a structure in the distal tubule, presumably at the macula densa area, is capable of sensing a physicochemical component of the fluid emergн ing from the ascending loop of Henle and of initiating a sequence of events that culminates in the local adjustment of vascular resistance (37, 50, 59, 60). Mild to substantive disagreement has met virtually every aspect of this hypothesis including (a) the nature of the intraluminal constituent in the distal tubule responsible for initiating feedback signals,(b) the mechanism of communication between the tubular cells and the vascular elements,(c) the factor responsible for eliciting changes in vascular tone,(d) the precise vascular element or elements most responsive to feedback signals, and (e) the physiological role of the feedback mechanism. In this review we evaluate