A three-dimensional (3-D) time-domain boundary integral equation method (RTEM) is presented for transient elastodynamic crack analysis. A non-hypersingular traction BIE formulation is used with the crack opening displacements and their derivatives as unknown quantities. A collocation method in conjunction with a time-stepping scheme is developed lo solve the non-hypersingufar time-domain HTEs. To simplify the analysis and to describe the proper behaviour of the unknown quantities at the crack front, a constant spatial shape function is appiierl for elements away from the crack front, while a spatial 'square-root' crack-tip shape function is adopted for elements near the crack front. A linear temporal shape function is used in the time-stepping scheme, Numerical calculations have been carried out for penny-shaped and square cracks. Results for the elastodynamic stress intensity factors are presented as functions of the temporal and the spatial variables. For the test examples considered, good agreement between the present results and those of other authors is obtained.