A collaborative ring trial of the part filter method was completed in 2011 by the CORESTA Smoking Behaviour Sub-Group. The primary objective of the ring trial was to gain a measure of the repeatability and reproducibility of estimated nicotine yields across participating laboratories using the part filter method. Secondary objectives were to gain a measure of the repeatability and reproducibility of estimated nicotine-free dry particulate matter (NFDPM) yields from tip UV absorption and tip solanesol, and to determine whether estimation of NFDPM from the measurement of tip solanesol is equivalent to the estimation of NFDPM from the measurement of tip UV absorption.