Guide catheters which can be used in percutaneous myocardial revascularization (PMR) to deliver therapeutic catheters to difficult to reach heart chamber wall regions. Some guide catheters include distal regions which can be bent under control from the proximal region of the catheter. One steerable guide catheter has a flexible distal region, a more proximal, less flexible intermediate region, a first lumen for receiving a therapeutic catheter, and an elongate manipulation member slidably disposed in a second, blind lumen. The elongate manipulation member can be secured off-center near the distal end of the flexible distal region. The distal region can be bent by retracting the manipulation member and straightened by pushing the manipulation member. Controllably bendable guide catheters according to the present invention can be nested inside other, similar guide catheters. The invention also includes means for resisting free rotation of guide catheters relative to other adjacent catheters or tubes.