This study aims at identifying potential predictors of clinical response and functional outcome in 101 neuroleptic-refractory patients with a DSM-III-R diagnosis of schizophrenia (N = 34), schizoaffective disorder (N = 30) or bipolar disorder with psychotic features (N = 37), naturalistically treated with clozapine over a 48-month period. The "clinical response" and "functional outcome" criteria were respectively defined a priori as: a reduction of at least 50 % in the Brief Psychiatric Rating Scale total score in one evaluation with respect to baseline; and a Global Assessment of Functioning Scale score of at least 50. Several clinical and socio-demographic variables were assessed at baseline and only the diagnosis of bipolar disorder was significantly related with the clinical response. Variables significantly related with the functional outcome were female gender, university education and early age at onset.