Blood dyscrasias, other than agranulocytosis, have received little attention in clozapine-treated patients. The aim of the present study was to shed more light on the incidence and course of clozapine-induced blood dyscrasias that occur during the first eighteen weeks of treatment with the antipsychotic. The study included 135 patients (M 75 and F 60), with a mean age of 33.1±10.4 years. The blood dyscrasias appeared in 88.1% of the total sample and were divided, on the basis of their duration, into transient and persistent. The analysis of data revealed that persistent dyscrasias had a higher incidence (56.2%) when compared to transient ones (11%). Persistent anemia was more common in female patients (F 52.5% vs M 11.2%), while male patients had a higher frequency of eosinophilia (M 26.2% vs F 21.2%), neutrophilia (M 18.7% vs F 15.0%) and leucocytosis (M 21.2% vs 8.7% F). The correlation between clinical response and blood dyscrasias revealed a statistically significant positive effect for male patients with eosinophilia (p< .05) and a negative correlation for male patients who presented persistent leucocytosis (p< .05). Our data could be offered to alert clinicians to the possibility that hematologic complications, other than agranulocytosis, may be common in clozapine-treated patients.