Purpose: To compare immediate and conventional loading of fixed full-arch maxillary prostheses supported by implants placed in healed and fresh postextraction sites. Materials and Methods: This prospective, controlled, nonrandomized 12-month study included 30 consecutive patients requiring fixed full-arch maxillary prostheses supported by implants placed in healed and fresh extraction sites. Fifteen patients were treated with conventional loading (control group), and 15 were treated with immediate loading (test group). Each patient received six to eight implants; implants with insertion torque 35 Ncm were conventionally loaded and excluded from the analysis. Implant success, biologic and prosthetic complications, success of the immediately loaded provisional prostheses, and marginal bone loss were assessed and analyzed statistically. Results: One test group patient failed to attend recall visits and was excluded from the study, and 16 implants did not achieve insertion torque of 35 Ncm and were excluded from analyses. The final sample included 29 patients and 193 implants (94 test implants, 99 control implants). Implant success rates were 96.8% (test) and 99.0% (control). In the test group, the most common complications were screw loosening and tooth fractures; in the control group, dentures caused discomfort and soft tissue irritation. The success rate of the immediately loaded prostheses was 100%. Average bone loss was 0.61 ± 0.21 mm for test implants and 0.53 ± 0.18 mm for control implants. Differences between loading protocols were not statistically significant. Conclusions: No significant differences in implant success and peri-implant marginal bone loss were seen in the current 12-month comparison of immediate and conventional loading of maxillary fixed full-arch prostheses. Biologic and prosthetic complications were rare with both loading protocols, and all immediately loaded provisional fixed prostheses performed successfully. Keywords: full-arch prosthesis, immediate implants, immediate loading