High performance liquid chromatography (HPLC) method for the determination and validation of a new non-steroidal anti-inflammatory agent, butibufen (CAS 55837-18-8), microencapsulated butibufen and its pharmaceutical forms--tablets, sachets (microencapsulated butibufen with excipients), microemulsion and cream--is described. Acetonitrile proved to be the best solvent for the extraction of butibufen from its pharmaceutical forms. The results submitted in this paper suggest that the HPLC method for the quantitative determination of butibufen is linear, accurate, precise and sensitive.