The R-curve and stress-strain behaviors in a variety of ferroelastic polycrystalline ceramic compositions are investigated and compared. These include soft and hard compositions of Pb(Zr,Ti)O-3, Na0.5Bi4.5Ti4O15, PbNb2O6, PbTiO3, and Pb(Mg1/3Nb2/3)O-3-Pb(Zr,Ti)O-3. The fracture toughness enhancement is the highest in the soft PZT ceramic. The material parameters which influence the ferroelastic contribution to the toughness enhancement are extracted from the stress-strain behavior and compared with the measured toughness enhancement. Limited ferroelastic toughening is expected in the PbNb2O6 and Na0.5Bi4.5Ti4O15 compositions yet they exhibit a relatively large toughness enhancement. This toughness enhancement is attributed to frictional crack bridging through an exceptional intergranular fracture path. The frictional bridging effects are relieved by thermal annealing indicating some ferroelastic assistance in this mechanism.