The performances of paranoid schizophrenic patients (No. = 10) and long-term undifferentiated schizophrenics (No. = 10) were compared on a series of problem-solving tasks. On all problems, the observed differences were in favor of the nonparanoid patients. Rigidity of internal representation of the task was suggested by the paranoid subjects' loss of efficiency in performance when a change in set was required. Their poor performance also resulted from their highly atomistic responses. The nonparanoid subjects, on the other hand, were oriented toward the more abstract, more efficient conceptualization associated with testing collections of entities.