Some implementation aspects of Iterative Learning Control (ILC) are considered. Since the ILC algorithm involves filtering of various signals over finite time intervals, often using non-causal filters, it is important that the boundary effects of the filtering operations are handled in an appropriate way when implementing the ILC algorithm. The paper illustrates in both theoretical analysis using the matrix description and in simulations of a twomass system that the method of implementation for handling the boundary effects can have large influence over stability and convergence properties of the ILC algorithm.