The objective of this paper was to analyze the crystal aspect ratio (AR), the fracture toughness, and the fractal dimension of 3BaO . 5SiO(2) glass-ceramics and to relate the topography of fracture surfaces to fractal behavior. These analyses demonstrate that crystal morphology strongly affects the fracture path, the fracture toughness, and the fractal dimension. Fracture toughness increased from 0.7 +/-0.1 MPa.m(1/2) for the glass to 2.2 +/- 0.6 MPa.m(1/2) for the glass-ceramic with an AR of 8.1 while the fractal dimensional increment (D*) for the glass and the glass-ceramic increased from 0.10 +/- 0.01 to 0.25 +/- 0.02, respectively. The materials with lower aspect ratios (AR = 1.4 and 3.6) exhibited the predicted relationship between toughness and D* while the glass-ceramic with an aspect ratio of 8.1 did not satisfy the expected relationship because of multiple toughening mechanisms.