Polyborosilazanes (PBSZs) were synthesized by co-ammonolysis of 2,4,6-trichloroborazine and dichloromethylsilane and used as precursors for Si-B-C-N ceramics. The pyrolyzed products were characterized with Fourier transform infrared, X-ray photoeletron spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction, and scanning electron microscopy (SEM). The results indicated the content of B or Si plays an important role in controlling the high temperature behavior of the precursors. The resistance of the ceramics, which were obtained from pyrolysis of PBSZs at 1500 degrees C, toward oxidative attack up to 1000 degrees C was also investigated by TGA and SEM/EDX. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 3400-3406, 2010