We have reviewed the development of Thurau's hypothesis that angiotensin mediates the effector responses of distal tubuloglomerular feedback-induced changes of nephron function. Several studies attempting to correlate responsiveness of the tubuloglomerular feedback system with intrarenal renin or juxtaglomerular renin contents have not delineated angiotensin's role in the feedback control system. Others and our own recent studies that have assessed the effects of acute blockade of the renin-angiotensin system on the responsiveness of tubuloglomerular feedback activity suggest that the effects of angiotensin are most likely a modulating influence on the activity of the system rather than the mediator of feedback-induced changes in glomerular function.