A new application of monoacidic dye is reported for the determination of pipethanate hydrochloride(PTH). The method is based on solvent extraction into chloroform of an ion-pair compound formed between methyl orange(MO) and PTH. PTH is determined by measuring absorbance of the extracts over the range of $2.0{sim}12.0{mu}g/ml$ at 420nm. Best accuracy can be obtained for solutions containing $3.0{sim}8.0{mu}g/ml$. The color was stable for at least 5 days. The molar absorptivity was $2.88;{ imes};10^4;l,;mol^{-1},;cm^{-1}$. Molar ratio and continuous variation plots have a maximum at 0.5 mol fraction of MO, indicating a 1 : 1 MO-PTH ratio.