Purpose: To assess the clinical 3-year outcome of prostheses supported by four immediately loaded zygomatic implants. Materials and methods: A total of 17 consecutively treated patients (7 men, 10 women, mean age 57.7 years) with severe maxillary atrophy were immediately rehabilitated with prostheses supported by four immediately loaded zygomatic implants. The patients were followed up for 3 years and the outcome measures included success rates of the prostheses, success rates of the zygomatic implants, complications and oral-health related quality of life (OHRQoL). Results: No patients dropped out. No prosthesis or zygomatic implants failed, though one implant was not used to support the final prosthesis because it emerged in an unfavourable position. Seven complications occurred: penetration of the orbital cavity during the drilling procedure with no relevant consequences; an infection followed by a fistula at one zygomatic implant, which was resolved with antibiotic treatment and surgical drainage; two patients developed sinusitis, and were successfully treated with antibiotics and meatotomy; fracture of the abutment screw occurred in one patient; and fracture of the prosthesis occurred in two patients and the definitive prostheses were repaired. The average score for the OHIP-14 questionnaire was 2.7, which was similar to that of the general population. Conclusions: The present 3-year study suggests that prostheses supported by four immediately loaded zygomatic implants can be used for successful rehabilitation of patients with severely atrophic maxillae. Keywords: alveolar bone loss/rehabilitation, dental implants, edentulous/rehabilitation, prospect ive studies, zygoma/surgery