Many peptides influence renal function and structure in physiological and pathophysiological situations. Bioactive peptides that regulate renal function and structure encompass various substances including vasopeptides, growth factors, cytokines and peptide hormones. We highlight some novel concepts indicating that the vasoactive peptides angiotensin II and endothelin-1 play a major role in the progression of renal disease. These effects may be amplified by reduced concentration of counteracting natriuretic peptides. In addition, recent evidence suggests that peptides such as leptin, previously not considered to exert any renal effects, may be involved in renal pathophysiology under certain conditions. One of the most imperative tasks in nephrology is to develop innovative strategies to slow the progression of chronic renal disease. Interference with the renal action of bioactive peptides will certainly be part of this strategy.