A sensitive, selective, accurate, precise and reproducible triple-quadrupole liquid chromatographic-mass spectrometric assay was developed and validated for BMS-181885 (I), a 5HT1 agonist, in human plasma using BMS-181101 as the internal standard (IS). The method involved solid phase extraction of plasma containing I and the IS using Isoelute CN cartridges. The supernatant was then evaporated to dryness at 40 degrees C. The residue was dissolved in 100 microL of the injecting solvent. The HPLC column was ODS-3, 2 x 100 mm. The mobile phase comprised 10 mM ammonium formate (pH = 4) and acetonitrile, 55:45 v/v, used in an isocratic condition. The mass spectrometer was programmed to admit the protonated molecules at m/z 461 (I) and m/z 370 (IS) via the first quadrupole filter and to select reaction monitoring of ions at m/z 152 for I and IS for the quantification. Standard curves were fitted to a weighted quadratic function over the concentration range 0.2-200 ng/mL. The lowest standard concentration (0.2 ng/mL) was experimentally established as the lower limit of quantitation of the assay. The mean predicted quality control concentrations deviated within +/- 11% of the corresponding nominal values; the intra-assay and inter-assay precisions were within 7.0% relative standard deviation. I was stable in the injection solvent at 4 degrees C for at least 24 h and for at least three freeze-thaw cycles. Freezer stability of I in plasma was demonstrated for at least 3 months. The extraction recovery of I was established as 97%. The validated assay was applied to a pharmacokinetic study of I in humans.