The present invention includes crystalline forms of N-acetylneuraminic acid (NeuAc) and crystalline forms of salts and/or solvates of N-acetylneuraminic acid (NeuAc). Furthermore, the present invention provides compositions comprising these crystalline forms and therapeutic use of the crystalline forms.本發明包括N-乙醯神經胺酸(NeuAc)之結晶形式以及N-乙醯神經胺酸(NeuAc)之鹽及/或溶劑合物之結晶形式。另外,本發明提供包含該等結晶形式之組成物及該等結晶形式之治療應用。