Background: Hyperhidrosis has a negative impact in quality of live, so effective and safe treatment options must be offered to patients. Objective: To evaluate effectiveness and adverse effects of botulinum toxin in primary focal hiperhidrosis. Material and method: An experimental open study in which 8 patients were selected from clinical practice with diagnosis of moderate to severe primary focal hyperhidrosis, who did not respond to aluminum hydroxide nor to oral anticholinergic drugs. Intradermal injection of botulinum toxin (Reage®) in 5 cases of axillar hyperhidrosis, 4 cases of palmar hyperhidrosis and 2 cases of facial hyperhidrosis. Minor test was performed before the procedure and at week 1 after procedure. Results: A qualitative reduction of sweating areas and good satisfaction with decreased sweating at week 1 after procedure were observed in every patient. Mean pain score was 3 for axilla, 6 for palms and 2 for face. Two patients presented ecchymosis in palms. Conclusion: Treatment of primary focal hyperhidrosis with botulinum toxin is effective and safe.