My dad is taking coumadin (warfarin) and both his legs are swollen and hot and painful to touch and he has a long red line going down one leg .?

Thrombophlebitis : Superficial thrombophlebitis is inflammation of a vein just under the skin, usually in the leg. A small blood clot also commonly forms in the vein, but is usually not serious. The condition usually settles and goes within 2-6 weeks. Treatments can ease pain or discomfort. Superficial thrombophlebitis is different to, and much less serious than, deep vein thrombosis. Still must be evaluated.

Go to the ER NOW: Maybe the Coumadin (warfarin) isn't working well or maybe he hasn't taken it or maybe he has had a bleed & a compartment syndrome, but whatever it is it sounds potentially life-threatening.