Introduction: Agranulocytosis is one of the most serious adverse effects of clozapine. The Latin American literature is currently scarce on the subject. Objective: To describe the occurrence of agranulocytosis or leukopenia secondary to clozapine and its associated factors in a sample of Chilean patients between the years 2011-2016. Materials and methods: An observational, retrospective type of study was designed base on virtual information from the National Pharmacovigilance Registry and definition of alarm levels according to the Technical Standard of clozapine, later performing statistical analysis. Results: total n 60patients, 8patients with some alarm event; Alarm I:5; Alarm II: 1; Alarm III: 2. Alarms were distributed between week 1 and week 242. The incidence was higher between weeks 0 and 12(1.26%). Until week 18, 53% of alarms I and 100% of alarms III occurred, alarm II occurred in month 10. Discussion: When comparing patients with and without alarm, significant differences were found in the basal count of leukocytes and neutrophils, with no differences in age and sex. Patients who presented alarms and/or lower baseline leukocyte or neutrophil counts could eventually benefit from a longer weekly follow-up. Conclusion: This study constitutes the first step towards exploring the adverse effects profile of clozapine in Chilean patients.