BACKGROUND Despite several research reports on incongruent psychotic features in mania, whether such features define a distinct disorder is unsettled. METHODS One hundred and fifty-five inpatients with mania according to DSM-III-R were systematically evaluated in order to collect demographic and clinical information. The symptomatological evaluation was conducted by means of the Comprehensive Psychopathological Rating Scale (CPRS) and the Scale for the Assessment of Positive Symptoms (SAPS). The presence/absence of incongruent psychotic symptoms at the index episode defined two subgroups of patients, whose familial, symptomatological, clinical and course characteristics were compared. RESULTS Eighty-six (55.5%) patients presented mood-incongruent psychotic features (MIP+). When this group was compared with the remainder of manic patients without such features (MIP-), we found substantial similarities in most demographic, familial and clinical characteristics. Despite these fundamental similarities, 4% of MIP+ vs 0% of MIP- had family history for schizophrenia (p < 0.05). We also observed a longer duration of the current episode, a higher percentage of chronic course, more suicide attempts and hospitalisations in MIP+. Moreover, other than psychotic symptoms, MIP+ showed more frequently depressive features and hostility. They also reported higher scores in social disability, especially in family and social settings. CONCLUSIONS Although our findings suggest that incongruent psychotic features in the main do not distinguish two separate entities--and can be considered as hallmarks of overall severity of mania--in a small minority of cases such features appear linked to familial schizophrenia. The numerous overlapping clinical characteristics in MIP+ and MIP- raise questions about the general nosographic utility of this categorisation.