Mosapride citrate, a selective serotonin 5-HT4 agonist, is a novel and potent gastroprokinetic drug. So far no assay procedure has been reported for the estimation of this drug either in bulk drug samples, pharmaceutical formulations or in biological samples. A rapid and sensitive high-performance liquid chromatographic method was developed for the estimation of mosapride citrate in bulk drug samples and pharmaceutical dosage forms. Risperidone was used as an internal standard (ISD). A HPLC system consisting of gradient pump, reverse phase C-18 analytical column, a variable UV-visible detector set at 274 nm and an integrator was used. The mobile phase consisted of acetonitrile: 0.02 M potassium dihydrogen phosphate buffer (pH adjusted to 4.0 with o-phosphoric acid) in the ratio of 50:50 (v/v), and was pumped at 1 ml/min at 40 degreesC. The drug and ISD were eluted at 8.10 and 2.27 min, respectively. The peak drug/ISD area ratio versus drug concentration relationship was linear (r = 0.9998). The method was validated for its linearity, precision and accuracy. The calibration curve was linear in the range of 0.5 to 30 mug/ml. The lower detection limit was found to be 0.23 mug/ml. The intra- and inter-day variation was found to be less than 1% showing high precision of the assay method. The mean recovery of the drug from the solutions containing 2, 4 or 10 mug/ml was 101.55 +/- 0.97% indicating high accuracy of the proposed HPLC method.