In this paper, fiber-like and dispersible tobermorite (Ca(5)(Si(6)O(16))(OH)(2).4H(2)O), 80-120 nm in diameter and up to tens of micrometers in length was prepared by a hydrothermal microemulsion method. In vitro bioactivity of the nanofibers were evaluated by examing the hydroxyapatite (HAp) forming ability on the surface after soaking in simulated body fluid (SBF) for various periods. After soaking in SBF, the nanofibers were completely covered by bonelike hydroxycarbonate apatite (HCA) layers, and the nanofibers after soaking still kept stability in fibrous morphology. The dissolution of the nanofibers reached about 24.5% after soaking in SBF for 14 days. The results suggested that the tobermorite nanofibers exhibited certain desirable characteristics, including bioactivity, degradability and stability in morphology, and are a potential candidate for a reinforcement material in the development of novel bioactive and degradable composites for biomedical applications.