Tolerances, the allowance on dimensional and shape variation of a design, are essential features of the design. As such, they should be present in the virtual prototype world of MCAD. The checking and fine-tuning of tolerances is a painstaking task, which has become easier with advanced dedicated software. The newest trend is to integrate the dedicated expert software systems in the MCAD software. This paper investigates in the solutions offered to designers and engineers to tolerance-model their designs from within the MCAD software.