Technical Abstract: This report describes the development of a robust method for studying the metabolism of B-carotene-d8 in humans using a combination of liquid chromatography/ particle-beam-mass spectrometry (LC/PB-MS). The utility of the LC/PB-MS method was demonstrated in a pilot study. The carotenoids were extracted from plasma into hexane and separated by reverse phase high-performance liquid chromatography (HPLC) using a C-18 column. The HPLC solvent was removed under vacuum within the dual-stage particle-beam interface. The de- solvated carotenoids were ionized in the negative-ion mode using methane chemical ionization and detected using selected ion monitoring. The limit of detection of the method was on the order of 0.3 ng (approximately 0.6 pmol) for B-carotene. B-Carotene-d8 was quantified in the plasma over a concentration range of two orders of magnitude using B-carotene-13C40 as an internal standard. The overall coefficient of variance (CV) for determining the concentration of the analytes from 30 ul of plasma was 3.9% for b-carotene and 2.4% for B-carotene-d8. The simplified experimental design having both high sensitivity and a high sample through-put makes large comprehensive studies feasible.