Supraventricular tachycardia (SVT) was induced in 7 patients by programmed cardiac stimulation via an esophageal lead. Blood pressure, renal function, and hormonal factors were measured before, during, and after SVT. The glomerular filtration rate increased during SVT, while renal blood flow did not change. The parameters of glomerular hemodynamics were calculated according to the method of Gomez. Glomerular pressure was 64±3 (mean±SE) mm Hg before SVT, and rose significantly (p<0.01) to 76±5 during SVT. This rise in glomerular pressure was associated with a decrease in afferent vascular resistance (from 3355±610 to 1770±517 dynes×sec/cm⁵, p<0.05) and an increase in efferent vascular resistance (from 3726±758 to 4814±780 dynes×sec/cm⁵, p<0.05). Since atrial natriuretic peptide (ANP) increased during SVT (from 40±15 to 208±72pg/ml, p<0.01), these changes in glomerular hemodynamics may be attributed to the physiologic action of ANP. Despite the changes in glomerular hemodynamics during SVT, natriuresis appeared after SVT and not during SVT. This suggests that natriuresis accompanying SVT could not be attributed to the changes in glomerular hemodynamics.