Well-known and standard techniques exist for the determination, from gas sorption data, of key characteristic parameters of porous heterogeneous catalysts, such as the specific surface area (BET), pore-diameter distribution (BJH), and pore connectivity (percolation analysis). However, at present, there are no methods to determine the pore-length distribution. Many previous mathematical modelling studies have shown that the nature of the relationship that exists between pore diameter and pore length heavily influences the rate of mass transport processes in porous solids, such as heterogeneous catalysts. Hence, a major obstacle to the proper implementation of pore-network models to study coupled diffusion and reaction processes in catalysts is the lack of a method for determining the pore-length distribution. This paper presents a new analytical method to determine the pore-length distribution from the results of novel experiments using the recently introduced integrated nitrogen sorption and mercury porosimetry technique. The analysis also, simultaneously, delivers improved estimates of pore connectivity and lattice size. (C) 2004 Elsevier Inc. All rights reserved.