A gas chromatography with flame ionization detection was developed to measure tranylcypromine in rat urine. The method involves extraction of the drug and the internal standard, phenylpropylamine from the urine using ethyl acetate and back extraction into 0.5N $H_{2}SO_{4}$. Following final extraction using dichloromethane, both the drug and the internal standard were converted to trifluoroacetyl derivatives and analyzed using a column of 3% SE-30 on 80/100 mesh Chromosorb W(HP). A calibration curve was constructed in the range of $5~50{mu}g$tranylcypromine sulfate in 0.5ml urine and found to be linear. The detection limit was $2{mu}g$. The tranylcypromine could be analyzed with the percent recovery of $100.81{pm}8.13$ (SD) ina concentration range of $8-40{mu}g$ in 0.5ml urine. When 0.4mmol/kg dose of the drug was administered through, an oral route, excretion percent of tranylcypromine in rat urine over 36hr was found to be $11.90{pm}6.04$ (SD) for tranyleypromine sulfate and $2.23{pm}0.63$ (SD) for benzyl trans-2-phenylcyclopropanecarbamate.