The disassembly line balancing problem is studied under uncertainty. Disassembly task times are assumed random variables with known probability distributions. An AND/OR graph is used to model the precedence relations among tasks. The goal is to assign the disassembly tasks to workstations while respecting precedence and cycle time constraints. The objective is to minimize the total line cost including the incompletion cost arising from task incompletion within the cycle time. A stochastic linear mixed integer programming formulation is developed.