Development of contraceptive implant methods, when based on established or on new synthetic chemical entities, is a decadal or multi-decadal process. The process often requires the cooperation of numerous investigators for laboratory work, for early Phase II trials, for dose-finding trials, and for Phase III clinical trials. The Phase III work also requires cooperation with a commercial manufacturer and potential distributor of the product. The Population Council has recently completed developmental work on two levonorgestrel-releasing implants, with filings to regulatory agencies that support extended use of Jadelle implants for 5 years and Norplant implants for 7 years. When the developmental process includes establishing the clinical properties of a molecule not yet approved by regulatory agencies, the minimum development time appears to be two decades. The status and rationale of studies of a new Nestorone-releasing, single implant developed by the Population Council for a period of use of 2 years are presented.