Using transmission electron microscopy (TEM), we have analyzed stacking fault pyramids found in multiple implant silicon-on-insulator material. From a comparison of computer simulations with weak-beam TEM images, and from the constraints imposed by crystallography, we have found that the Burgers vectors of the pyramidal stair-rod dislocations are edge dislocations with the Burgers vector 1/3[100]. We have also determined that the stacking faults in these pyramids are intrinsic, and therefore probably formed through vacancy condensation.