Whisker-reinforced zirconia-mullite ceramic articles exhibiting excellent high-temperature modulus of rupture strength and good toughness are provided from batches comprising the free oxides ZrO.sub.2, SiO.sub.2 and Al.sub.2 O.sub.3 in combination with SiC whiskers for reinforcement. Due to the fine oxide particle sizes attainable and the fact that the mullite is formed in situ in the consolidation process, dense, whisker-reinforced mullite composite articles exhibiting excellent high-temperature strength and toughness may conveniently be obtained.