The concept of secret use has been a difficult element in establishing whether the validity of a patent may be challenged. Its difficulty is entrenched in the uncertainty of interpretation of the construction of the legislation and the meaning that the legislature imparts on it. One of the main cases in Australian patent law that has tested the issue of secret use is Azuko Pty Ltd. v. Old Digger Pty Ltd. (2001) 52 IPR 75. The significance of this decision is the differing approaches to the issue of secret use. This case demonstrates the various practical and policy implications that arise out of the differing views from the judgment. This paper will discuss the practical and policy implications raised by the differing views of the judges.