Endothelin plays an important role in cardiovascular pathology. As one of the most important endothelium-derived vasoconstrictor substances, endothelin together with endothelium-derived vasodilating factor control vascular tone and contribute to the vasoconstrictory response if the production of endothelium-derived vasodilating factor is impaired. The aim of the study was to assess the changes of the local endothelin level in coronary circulation immediately after percutaneous transluminal coronary angioplasty (PTCA). Plasma endothelin levels were measured in blood samples from the peripheral vein and ostium of the coronary artery before the angioplasty, and from the distal coronary artery just beyond the dilated segment and the peripheral vein immediately after the procedure. The plasma endothelin level was significantly higher in the ostium of the coronary artery already prior to PTCA as compared to the peripheral vein (10.9 ± 3.4 vs. 7.2 ± 2.1 pg/ml, p < 0.005). There was no change in the endothelin level in the coronary artery distal to the dilated segment immediately after the procedure as compared to the initial level, although this level was higher than the postangioplasty venous level (9.8 ± 2.9 vs. 7.7 ± 2.0 pg/ml, p < 0.005). Individual changes in coronary-artery plasma endothelin levels as a response to coronary angioplasty were disparate. An increase and a decrease in coronary artery plasma endothelin levels by more than 2 pg/ml after coronary angioplasty were observed in 3 and 6 subjects, respectively. In conclusion, increased plasma endothelin levels were found in blood samples drawn from the coronary artery as compared to the peripheral vein. There was no further change in the plasma endothelin level in the coronary artery distal to the dilated segment after angioplasty; however, the individual responses were disparate.