An experiment is reported examining the role of attention and expertise in multiple target tracking. It compares the ability of professional radar operators (experts) and undergraduate students (novices) to acquire and track subsets of randomly moving targets amongst distractors, and respond appropriately to a probe. Participants undertook this tracking task alone then, subsequently, in conjunction with a second, digit categorization task. For half the participants, the second task commenced prior to the tracking task's target acquisition phase, for the remainder after. Results suggest experts are better than novices across all conditions. Further, a comparison of results between the two dual task conditions indicates that attentional resources make a contribution to target tracking in both novices and experts, but only appear to make a contribution to target acquisition in novices. The results have implications for theories of multiple target tracking; the selection of radar operators; and the monitoring of their training. Copyright © 2004 John Wiley & Sons, Ltd.