A method for generation of a three-dimensional, time-dependent turbulent inflow condition for simulation of spatially-developing boundary layers is described. Assuming self-preservation of the boundary layer, a quasi-homogeneous coordinate is defined along which streamwise inhomogeneity is minimized (Spalart 1988). Using this quasi-homogeneous coordinate and decomposition of the velocity into a mean and periodic part, the velocity field at a location near the exit boundary of the computational domain is re-introduced at the in- flow boundary at each time step. The method was tested using large eddy simulations of a flat-plate boundary layer for momentum thickness Reynolds numbers ranging from 1470 to 1700. Subgrid scale stresses were modeled using the dynamic eddy viscosity model of Germano et al. (1991). Simulation results demonstrate that the essential features of spatially-developing turbulent boundary layers are reproduced using the present approach without the need for a prolonged and computationally expensive laminar-turbulent transition region. Boundary layer properties such as skin friction and shape factor as well as mean velocity profiles and turbulence intensities are in good agreement with experimental measurements and results from direct numerical simulation. Application of the method for calculation of spatially-developing complex turbulent boundary layers is also described.