Blood dyscrasias, other than agranulocytosis, have received little attention in clozapine-treated patients. The aim of the 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. These dyscrasias have been characterized on the basis of different variables (patient gender, age, number of previous hospitalizations; time of appearance and disappearance, dose of clozapine when blood dyscrasias appeared and at the end of the 18th week of treatment, drugs used before and concomitantly to clozapine treatment, correlation with clinical response). 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). 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.