Purpose: The aim of this clinical study was to determinate if patients allergic to penicillin present a higher incidence of dental implant failure compared with nonallergic patients. Materials and Methods: This crosssectional clinical study analyzed patients rehabilitated with endosseous dental implants between September 2011 and July 2015, at the University Dental Clinic, School of Dentistry, International University of Catalonia (UIC). Prophylactic antibiotic therapy was prescribed for all patients: a single dose of 2 g of amoxicillin taken orally 1 hour before implant surgery for non-penicillin-allergic patients, and 600 mg of clindamycin taken orally 1 hour before the implant surgery for penicillin-allergic patients. Postsurgical antibiotics were prescribed to prevent early implant failures and postoperative infections: amoxicillin 750 mg three times a day for 7 days for nonallergic patients, and in patients with penicillin allergy, 300 mg clindamycin every 6 hours for 7 days. Implant failure was defined as the removal of the implant for any reason and was classified as early or late failure. Results: A total of 1,210 patients' files were analyzed; 8.03% of nonallergic patients and 24.68% of penicillin-allergic patients presented at least one implant failure. In penicillin-allergic patients, 21.05% were classified as late implant failure and 78.95% as early implant failure, with a lack of osseointegration (80%) being the mean reason for an early implant failure. Penicillin-allergic patients demonstrated a higher risk of implant failure with a risk ratio of 3.84 (95% CI) compared with nonallergic patients. Conclusion: Penicillinallergic patients treated with clindamycin presented almost four times the risk of suffering dental implant failure, although other variables such as implant brand, location, and the surgeon's skill might have influenced these results. Keywords: clindamycin, dental implant, implant failure, implant osseointegration, penicillin allergy