The process of relational control, that is, the negotiation of "who's in charge," was examined in 40 families of persons with schizophrenia and bipolar disorder. Verbal interaction recorded during problem-solving tasks was coded with the Relational Control Coding System (RCCS). Patterning of message and response sequences was compared by diagnosis of the patient and level of expressed emotion (EE) of the family. Results indicated that patients with either diagnosis assert control more than their parents, that high-EE families compete for control more than low-EE families, and that families of bipolar patients compete for control whatever their EE status. The most dramatic differences in control patterns were in the dual-parent, high-EE families of persons with schizophrenia, in which the patients successfully challenged parents for control, and parents often yielded. It was concluded that EE reflects transactional processes in families that vary by diagnosis of the patient.