We operationalized and tested E. R. Hilgard's (1973a, 1977b) neodissociation theory. His work suggested that the dissociation necessary for experiencing hypnotic phenomena may be attributable to a general capacity for dissociation that should be measurable outside of the domain of hypnosis. We used several types of operational definitions and tasks in order to capture a wide range of meanings. The performances of 169 undergraduates on clerical/motor and cognitive tasks in selective attention and divided attention conditions, as well as the degree of incidental learning, were correlated with scores on the Harvard Group Scale of Hypnotic Susceptibility. The results do not support a neodissociation theory despite the study's respectable convergent-discriminant validity. Although conceptual and methodological considerations were noted, the results may indicate an important limitation of the explanatory power of E. R. Hilgard's neodissociation theory.