Patient Boswell, who is severely amnesic for both retrograde and anterograde material, can provide the correct state name for a particular city, given the name of the city, e.g. given 'Denver' he will respond 'Denver ... Colorado', an ability that, by itself, would suggest that he knows about each item in the set and about their connection. However, he cannot name cities in a state, and he is unable to provide even superficial information about the unique characteristics of most cities and states. We investigated this phenomenon with several experiments. In the first (State Completion), Boswell was given names of cities in the U.S.A., and asked to provide the associated state name; in the second (City Generation) we asked him to provide names of cities located in particular states. For State Completion, Boswell correctly supplied state names for 53% of the items, and he improved to 94% correct in a forced choice paradigm. For City Generation, his performance was markedly inferior to that of controls; in fact, he produced only 4 city names for a total of 27 different states. In another experiment, in which Boswell was asked to give specific characteristics of cities and states, he was also severely defective. The dissociations suggest that the ability to complete a well-learned verbal set (e.g. Denver-Colorado), given its first component, implies nothing about (1) the underlying verbal or non-verbal knowledge associated with either item in the set, or (2) their relationship to one another. The maintenance of this ability depends on a circumscribed cortical region of the dominant hemisphere, which includes Brodmann's field 22 and part of fields 21 and 37.