An efficient sample extraction and cleanup method was developed for determination of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in eggs. The procedure included solvent extraction of HMX from eggs followed by cleanup using florisil and styrene-divinylbenzene (SDB) cartridges. Homogenized egg aliquots were thoroughly mixed with 10 mL acetonitrile and extracted with ultrasonication for 1 h. Each sample was centrifuged and all liquid was collected for cleanup. After concentration by N2 evaporation, each extract was cleaned by florisil and SDB cartridges to remove endogenous interfering compounds. Finally, each extract was filtered through a 0.2 μm PTFE membrane and stored for liquid chromatographic-mass spectrometric (LC-MS) analysis. Chromatographic separation was achieved on a reverse phase (RP) C18 column, with a mobile phase containing 60% methanol + 40% 1.0 mM acetic acid aqueous solution. Acetic acid was employed as mobile phase additive to form negatively charged adduct ions [M + CH3COO]-, and m/z = 355 was quantified by selective ion monitoring (SIM). Overall recoveries from eggs containing 10, 50, 250 and 1000 ng/g of HMX were 84.0%, 88.0%, 90.6% and 87.4%. A method detection limit (MDL) of 0.15 ng/g was achieved.