The objective of the research was to propose and validate a theoretically meaningful link between three constructs of hierarchical menu design: menu dimension, task complexity, and user knowledge structure. Twenty-four subjects participated in a nested factorial experiment. The subjects performed a menu retrieval task using a hierarchical menu system constructed for use in the domain of utility boiler control. The dependent variables were time to respond and accuracy. The independent variables were menu dimension, task complexity and user knowledge structure. Four hypotheses were tested. The foundation of the hypotheses was based upon the premise that when task complexity is low, the short-term memory requirements of the menu retrieval task are low. Thus, the user's knowledge structure will not affect performance because it is not required for the chunking of visual information. The objectives of this research were met and are presented in the context of an information processing model for psychomotor tasks.