We developed a U-shaped diagnostic and guiding catheter for left coronary angiography and angioplasty. Angiography with a 6 French (F) diagnostic U-shaped catheter was attempted in 101 patients (pts). Primary use in 82 pts; all successful. Secondary use after failure of 6 F left Judkins diagnostic catheters to intubate the left main coronary artery in 19 pts; 17 successful. An 8 F U-shaped guiding catheter was used for percutaneous transluminal coronary angioplasty (PTCA) of left coronary artery branches in 102 pts [left anterior descending (LAD), 48 pts; circumflex (CX), 54 pts]. Stable cannulation of the left coronary artery was achieved in 96 pts (94%), but PTCA was successful in 90 pts (88%). Primary use in 70 pts (LAD, 27 pts; CX, 43 pts). PTCA was successful in 60 pts. Secondary use after failure of left Judkins and Amplatz guiding catheters in 32 pts (LAD, 21 pts; CX, 11 pts). PTCA was successful in 30 pts. No complications were seen. In conclusion, U-shaped diagnostic and guiding catheters increased the success rate of 1) left coronary angiography after failure of left Judkins diagnostic catheters; and 2) PTCA of the left anterior descending and circumflex arteries after failure of left Judkins and Amplatz guiding catheters.