In induction welding of thermoplastics, induction heating of a gasket, made of a ferromagnetic-powder-filled bonding material and placed at the interface of thermoplastic parts to be joined, is used to melt the interface; subsequent solidification of the melt results in a weld. Tensile tests on induction butt-welds of polycarbonate (PC), poly(butylene terephthalate) (PBT), and polypropylene (PP) are used to characterize achievable weld strengths, and microscopy is used to correlate weld strength with the morphology of failure surfaces. In PC, PBT, and PP relative weld strengths as high as 48%, 43%, and 55% of the respective strengths of PC, PBT, and PP have been demonstrated. Relative weld strengths on the order of 20% have been demonstrated in PC-to-PBT welds.