At what point do you call a riv bet HU w. A high?

[Harv72b]

It's entirely read-dependant. Against some opponents I'll call with A high every time. Against others I'll fold without a second thought even if the pot is laying me 20:1. Against unknowns, I generally follow the same 10:1 guideline, assuming I have a good kicker.

Where the big leak often comes in is when you're calling too many turn bets or raises with A high. In most pots and against most opponents, you can give up your A high hand on the turn if they show aggression.