VSD+ is a model to calculate effects of atmospheric deposition and climate change on soil acidification,nutrient availability and carbon sequestration. The model has been developed to support emission abatementstrategies of sulphur (S) and nitrogen (N) in Europe. This document contains a summary of the modeltheory, technical documentation and descriptions of testing, validations and the sensitivity analysis of themodel. The processes described in the paper about VSD+ have been tested successfully. The sensitivityanalysis showed that the constant for the equilibrium between H+ and Al3+ in the soil solution and theweathering rate of Ca are the parameters that to a large extent determine the value of the simulated pH. Forbase saturation, most important parameters are the exchange constant between H+ and base cations andthe weathering of Ca. For the C/N ratio of soil organic matter, litterfall of C and N and the uptake of N areimportant influencing factors. The nitrate concentration strongly depends on the leaching flux and the net N input.