Both testlet design and hierarchical latent traits are fairly common in educational and psychological measurements. This study aimed to develop a new class of higher order testlet response models that consider both local item dependence within testlets and a hierarchy of latent traits. Due to high dimensionality, the authors adopted the Bayesian approach implemented in the WinBUGS freeware for parameter estimation. A series of simulations were conducted to evaluate parameter recovery, consequences of model misspecification, and effectiveness of model-data fit statistics. Results show that the parameters of the new models can be recovered well. Ignoring the testlet effect led to a biased estimation of item parameters, underestimation of factor loadings, and overestimation of test reliability for the first-order latent traits. The Bayesian deviance information criterion and the posterior predictive model checking were helpful for model comparison and model-data fit assessment. Two empirical examples of ability tests and nonability tests are given. (Contains 6 tables.)