The aim of this study was to compare the thermal properties and microstructure of a new lithium-containing glass-ceramic to those of a dental glass-ceramic as control. The chemical composition of both control and experimental glasses was determined by electron microprobe analysis. The nucleation and crystallization temperatures were determined by differential thermal analysis (DTA). The glass specimens were submitted to various heat treatments and analyzed by X-ray diffraction (XRD) to determine the optimal conditions for nucleation and growth of the crystalline phases. UV-visible spectroscopy was used to study the nucleation of both glasses. The microstructure of the experimental glass-ceramic was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction. Results showed that optimal crystallization of the experimental glass-ceramic was achieved after heat treatment at 950 degrees C for 30 min. The microstructure of the experimental glass-ceramic exhibited mica platelets randomly oriented and highly interlocked. The mica was identified as taeniolite, a lithium-containing tetrasilicic fluormica.