Introduction: Rapid Adenosine Triphosphate (ATP) testing is becoming a commonly used method to measure cleanliness on reusable medical devices and healthcare environmental surfaces. Unfortunately, ATP testing devices suffer from inherent variability from a number of sources including imprecision in ATP measurement. Method: This paper proposes a new sampling algorithm which reduces the impact of inherent variability and thus improves decision making when using ATP testing. Conclusion: This algorithm can be applied across a variety of applications to provide more reliable data on measurable cleanliness standards for both medical devices and environmental surfaces. Formal trials using the new ATP sampling algorithm are required. ; 7 page(s)