1 financial resources between a government agency (Department of Veterans Affairs, Office of Dentistry) and private industry. The DICRG goals were simple: 1) to design and conduct cost-effective, scientific, and independent clinical studies in the area of endosseous implants, and 2) to facilitate the transfer of new information into the knowledge base associated with the clinical practice of implantology. In 1991, the DICRG activated the clinical study, “The Influence of Dental Implant Design, Application and Site of Placement on Long-Term Clinical Performance and Crestal Bone.” More than 85 dentists at 32 research centers were distributed throughout the United States. This study provides reliable scientific data that are universally important to dentists and edentulous patients worldwide concerning the clinical performance of implants of different designs and materials.1 The primary unit in the DICRG study is the prosthesis; the secondary is the implant. The primary hypothesis provided the basis for the development of the experimental design and the estimation of sample size. Together with the secondary hypotheses, it will guide the reporting of outcomes after 5 years of follow-up.1 The primary hypothesis is that the implant-supported prosthesis will be functional over a 5-year period in at least 90% of the cases treated in this study regardless of implant design, application, or location. The secondary hypotheses are as follows: 1. The success rates among implants with screw, cylinder, grooved, and basket designs will be the same over a 5-year period. 2. The success rates for implants used for edentulism, partial edentulism, and single-tooth replacement will be the same over a 5-year period. 3. The success rates for implants in the anterior versus posterior jaw and maxilla versus mandible will be the same over a 5-year period. 4. The losses of crestal bone around implants with screw, cylinder, grooved, and baskets designs will be the same over a 5-year period. 5. The complications and adverse responses experienced with different implant designs will be the same over a 5-year period. A “case” in these articles refers to the prosthesis supported by a single implant or up to six implants. A The American Academy of Periodontology is well recognized by the international dental community for its strong commitment to the advancement of the knowledge bases associated with periodontology and dental implantology. The Dental Implant Clinical Research Group (DICRG) is honored to have its interim (36 to 71 months) progress reports published in volume 5 of the Annals of Periodontology. The DICRG findings can be applied to most endosseous implant systems, to dentists of all skills and experience levels, and to most patients. These articles will: 1) provide clinicians with the latest scientific information related to many of the confounding variables that exist daily in the private office; 2) present some treatment options (e.g., implant designs and antibiotic use) that may have significant potential to prevent or reduce implant failures; and 3) provide other investigators with new and stimulating data that could lead to the development of new clinical studies. While many papers in this issue are based on 36month data, there are a few papers reporting data up to 71 months that may have smaller numbers because not all patients reached the evaluation period at the same time. This is due to patients being accrued at different points in the study. The reader must view the conclusions in the same context as the DICRG does with interest and caution at the same time. These findings beyond 36 months are included here since they represent some of the more controversial and clinically important questions associated with survival of endosseous implants of various designs. The DICRG designed a prospective clinical study to assess the effect or the value of a new treatment methodology in human subjects, whereby the treatment must be applied to all subjects in a standard manner and does not involve a control.