USP 23/NF 18 now includes two new apparatus (Apparatus 3 and 4) designed for the purpose of characterizing drug release from extended-release dosage forms. These new apparatus permit changes in media during the evaluation and expose the delivery system to different hydrodynamics. Apparatus 3, which is the focus of this experimental work, consists of 7 reciprocating cylinders that can be moved through multiple (6) rows of cylindrical vessels; dip rate, time, immersion in each row, and the specific media employed are primary factors which can be manipulated. The aim of this study was to validate and instrument and compare two calibrators e.g., USP Chlorpheniramine Extended-release Tablets (Drug Release Calibrator, single unit) and USP Theophylline Extended-release Beads (Drug Release Calibrator, multiple unitâ in Apparatus 3 using single and multiple row procedures. Despite the multiple row design, the Apparatus Suitability Test for both calibrators is conducted by sampling from vessels in a single row. This report comments on critical experimental procedures and demonstrates that results for both calibrators fall within specified limits when multiple rows of vessels are used.