Purpose: The aim of this study was to compare the survival of implants placed in mature bone with the survival of implants placed in fresh extraction sockets in the same patients. Materials and Methods: A retrospective study of patients treated simultaneously with at least one immediate and one nonimmediate implant was carried out for the period 2005 to 2008. Data were recorded for patient age and sex; implant length, diameter, and position; and, for postextraction implants, distance between the implant and the alveolar bone. Results: One thousand twenty-two implants were placed in 150 patients; 480 were placed immediately and 542 were placed in mature bone. The mean implant survival rate was 93.4%; survival rates were 93.8% for immediate implants and 93.2% for nonimmediate implants. The failure rate in the maxilla was 5.2% and in the mandible it was 2.8%. The failure rate for immediate implants in the posterior maxilla was 8.5%, which was statistically significantly higher than for implants placed elsewhere. Of the failed implants, 72% were early failures. Conclusions: The survival rate of implants placed in fresh extraction sockets was similar to that of implants placed in mature bone. A statistically significantly higher failure rate was seen with immediate implants placed in the posterior maxilla. Palabras clave: fresh extraction sockets, immediate dental implants, immediate implantation, implant survival rate