In two experiments, we examined the attentional mechanisms governing sensorimotor skill execution across levels of expertise. In Experiment 1, novice and expert golfers took a series of putts under dual-task conditions designed to distract attention from putting and under skill-focused conditions that prompted attention to step-by-step performance. Novices performed better under skill-focused than under dual-task conditions. Experts showed the opposite pattern. In Experiment 2, novice and expert golfers putted under instructions that emphasized either putting accuracy or speed--the latter intended to reduce the time available to monitor and explicitly adjust execution parameters. Novices putted better under accuracy instructions. Experts were more accurate under speed instructions. In agreement with theories of skill acquisition and automaticity, novice performance is enhanced by conditions that allow for on-line attentional monitoring (e.g., skill-focused or accuracy instructions) in comparison with conditions that prevent explicit attentional control of skill execution (e.g., dual-task or speed constraints). In contrast, the proceduralized skill of experts benefits from environments that limit, rather than encourage, attention to execution.