Rocha e Silva's utmost contribution to science was the isolation of bradykinin, a naturally occurring nonapeptide known to have a broad spectrum of actions. Amongst them, considerable evidence suggests that the diuretic effects of endogenous bradykinin are, in part, mediated by inhibition of vasopressin-stimulated water transport. This is true for both the mammalian renal cortical collecting tubule and the urinary bladder of the toad (functionally analogous to the tubule). A review of the main contributions that led to that knowledge is presented.