The STICS model simulates the behavior of soil–crop systems for a large range of crops. It is widely used for analyzing, evaluating, and designing cropping systems. Because of the complexity of such models, it is important to adapt methods and tools for analyzing, improving and evaluating them. This chapter presents software providing these services for the STICS model. Its main features are: (i) handling of multiple simulations, (ii) uncertainty and sensitivity analysis, (iii) parameter estimation, and (iv) comparison with observed data. Parameter estimation of crop models presents particular problems. The choice of an appropriate statistical model for model error is one of them. The software proposes options for choosing among a collection of possible assumptions concerning model error including zero or non-zero expectations, independent or correlated errors, known or unknown variances…These options are available both for the frequentist and Bayesian parameter estimation methods implemented. The software also includes special features specifically adapted to crop models, such as automatic procedure for parameter estimation in several stages and simultaneous estimation of varietal and specific parameters. Numerous indicators are provided to help the modeler analyze results. This software thus has two major objectives: (i) to help modelers using and improving the model and (ii) to allow one to compare various methods for parameter estimation on real problems. In this chapter we detail the design, features, and ways of using the software. In closing, we present examples of sensitivity analysis and parameter estimation applications with the STICS crop model.