We propose a model of "choice overload" which refers to a stronger tendency to select the default option in larger choice problems. Our main finding is a behavioral characterization of an asymmetric regret representation that depicts a decision maker who does not consider the possibility of experiencing regret for choosing the default option. By contrast, the value of ordinary alternatives is subject to regret. The calculus of regret for ordinary alternatives is identical to that in Sarver's (2008) anticipated regret model, despite the fact that the primitives of the two theories are different. Our model can also be applied to choice problems with the option to defer the decision.