The oxidation behavior of three precursor-derived ceramics Si4.46BC7.32N4.40 (AMF2p), Si2.72BC4.51N2.69 (AMF3p), and Si3.08BC4.39N2.28 (T2/1p)-was investigated at 1300 degrees and 1500 degreesC. Scale growth at 1500 degreesC in air can be approximated by a parabolic rate law with rate constants of 0.0599 and 0.0593 mum(2)/h for AMF3p and T2/1p, respectively. The third material does not oxidize according to a parabolic rate law, but has a similar scale thickness after 100 h. The results show that at least within the experimental times these ceramics develop extremely thin scales, thinner than pure SiC or Si3N4.