In immediate serial recall, participants are asked to recall novel sequences of items in the correct order. Theories of the representations and processes required for this task differ in how order information is maintained; some have argued that order is represented through item-to-item associations, while others have argued that each item is coded for its position in a sequence, with position being defined either by distance from the start of the sequence, or by distance from both the start and the end of the sequence. Previous researchers have used error analyses to adjudicate between these different proposals. However, these previous attempts have not allowed researchers to examine the full set of alternative proposals. In the current study, we analyzed errors produced in 2 immediate serial recall experiments that differ in the modality of input (visual vs. aural presentation of words) and the modality of output (typed vs. spoken responses), using new analysis methods that allow for a greater number of alternative hypotheses to be considered. We find evidence that sequence positions are represented relative to both the start and the end of the sequence, and show a contribution of the end-based representation beyond the final item in the sequence. We also find limited evidence for item-to-item associations, suggesting that both a start-end positional scheme and item-to-item associations play a role in representing item order in immediate serial recall.