The effect of fluorine (F) content in the parent glass on nucleation and crystallization of glass-ceramics with canasite as the principle crystalline phase have been studied using differential thermal analysis, X-ray diffraction, and transmission electron and scanning electron microscopies. CaF2 precipitation occurred during the nucleation phase at all concentrations studied. However, canasite formation during Subsequent crystallization was strongly dependent on F content. Canasite failed to form at both high and low concentrations of F, while with intermediate F concentrations canasite and CaF2 were the only phases identified. Agrellite (NaCa2Si4O10F) formed when the F content was high.