A new approach combining time lag and mass balance for determining the kinetic parameters in controlled release was proposed in order to minimize measurement errors due to actual experimental conditions deviating from idealities under which the time lag and mass balance analyses were developed. Basically, the permeation data were pre-screened for analysis with time lag and mass balance methods separately, and criteria for data screening were proposed. The upper time limit of short-time permeation data suitable for analysis with the time lag method was determined based on the extent of concentration variations across the membrane, and the onset time point of the long-time permeation data for analysis with the mass balance method was determined based on the time lag of the system. The permeation of ciprofloxacin hydrochloride through chitosan membranes was chosen as a model system to demonstrate the validity of this approach for evaluation of permeability and diffusivity. (C) 2010 Elsevier Ltd. All rights reserved.