In recent years, finite element modeling has become an important design tool. Advanced programs make it possible to use more complex soil models in addition to standard elasto-plastic models with Mohr-Coulomb failure criteria. These new models can follow nonlinear behavior and complicated loading sequences. The two most promising new models are: the Hardening Soil Model (HS) and the Soft Soil Model (SS). This paper focuses on the behavior of Transdanubian Clay, common in Hungary. Sampling, laboratory testing, and evaluation of data aiming at determining parameters for HS and SS models are described. Results based on oedometer tests using unloading/reloading sequences proved to be adequate for input to these models. © 2009 Akadémiai Kiadó.