Prospectively collected data on 19 recently hospitalized patients with bipolar disorder were examined for prodromal changes preceding relapse. The 4-month periods before six manic and six depressive relapses were compared with each other and with a comparable period for seven patients who did not relapse. The Brief Psychiatric Rating Scale was used to assess symptoms. Significant elevations in unusual thought content were found 1 month before manic relapse. Depressive relapsers evidenced higher levels of conceptual disorganization throughout the prerelapse period. Nonrelapsers showed very stable symptom profiles.