Genetic algorithm (GA) inversion, a nonlinear global optimization technique, has been applied to determine crustal and uppermost mantle velocity structure from teleseismic receiver functions. With a new modelling in which not only the S wave velocity but also the layer thickness and the VP/VS ratio are model parameters, the GA receiver function inversion is able to recover the velocity structure with reasonable accuracy in the whole crust, and particularly well for the surface layer and the crust-mantle boundary. Structural inversion for receiver functions from a network of broadband seismic stations in eastern Australia allows a comparison of crustal structure from different tectonic environments. The crust-mantle boundary is shallow and sharp on the craton but deep and transitional along the axis of the fold belt zone in eastern Australia. This suggests crustal thickening in the fold belt by underplating or intrusion of mantle materials into the lower crust. ¿ American Geophysical Union 1996