In 1996, the Danish audiological clinics and hearing aid manufacturers jointly developed a clinical procedure for testing novel hearing aids in a clinical setting. This endeavour cane about because it was being acknowledged that clinical testing of hearing aids was likely to become more prominent as a result of the more advanced signal processing schemes enabled by digital technology in particular. It was understood that future hearing aids would encompass a large variety of diverse features, and that a rigid and detailed test protocol would therefore be inappropriate. The procedure was therefore devised as a framework within which a test protocol can be developed, and constitutes the framework of good scientific and clinical practice.