Abstract: AIM　To study the metabolic chiral inversion and chiral metabolites of R-(-)-ibuprofen. METHODS　Following administration of R-(-)-ibuprofen (250 mg*kg^-1), analysis was performed on rat urine purified extracts obtained by solid phase extraction onto C-18 bonded silica gel, then the metabolites of ibuprofen were detected and identified by ¹HNMR spectroscopy. RESULTS　Except for a little ibuprofen, there were 2＇-hydroxy-ibuprofen and its glucuronide, 1＇-carboxy-ibuprofen glucuronide and ibuprofen glucuronide in rat urine. 2＇-hydroxy-ibuprofen is the main metabolite. 1＇-carboxy-ibuprofen glucuronide and ibuprofen glucuronide were diastereoisomers. CONCLUSION　There was the phenomenon of metabolic chiral inversion, whereby the R-enantiomer is transformed in vivo to its active S-antipode via an unusual process.