Background: A family of six cardiovascular hormones – atrial natriuretic peptide, brain natriuretic peptide, C-natriuretic peptide, long acting natriuretic peptide, vessel dilator and kaliuretic peptide – was investigated for the ability to decrease the number of human angiosarcoma cells. Methods and Results: Within 24 h, vessel dilator, long acting natriuretic peptide, kaliuretic peptide, atrial natriuretic peptide and their intracellular mediator cyclic GMP decreased the number of angiosarcoma cells by 61, 30, 29, 36 and 32%, respectively, and DNA synthesis by 68–85%. Brain natriuretic peptide and C-natriuretic peptide had no effect(s). The natriuretic peptide receptor C was present. Conclusions: Four cardiovascular hormones decrease the number of angiosarcoma cells within 24 h via inhibition of DNA synthesis mediated in part by cyclic GMP.