User-friendly software (DEPOSITION 2.0) has been developed which permits characterization of aerosol particle losses in transport systems. Tho sub-models which comprise the DEPOSITION code are presented and the limitations of these sub-models are noted. These sub-models have all been previously published in the peer-reviewed literature. The software can be used to determine the penetration aerosol through existing transport systems; it will provide the optimal tube diameter for a transport system operated at a given flow rate and at a given particle size; it will provide a value for the maximum penetration for a transport system that would connect two points in three-dimensional space; and it will provide tables of data and create output files for parametric studies on the effects of varying particle size, flow rate and tube diameter. Use of this software for specific examples is given herewith in an Appendix. Reference to this software is included in NRC Regulatory Guide 8.25 (1992) where it is considered to be an acceptable method for calculating the penetration of particles through sampling systems.