A malpractice insurance plan which involves an agreement by a professional society (such as a State medical society) to sponsor a particular insureds medical malpractice insurance coverage, and to cooperate with the insurer in the administration of the coverage. The cooperation may include participation in marketing, claims review, and review of ratemaking. Until 1975, this was the predominant approach to coverage. In 1975, a number of carriers with such arrangements announced they were withdrawing from them. They have been replaced by professional society operated plans, joint underwriting associations, State insurance funds and other arrangements.