The effects of silicon-functional isocyanates on the stability of oil-in-water emulsions with and without a carbon functional triisocyanate in the oil phase were investigated. The oil component was di-n-butyl-phthalate (DBP) containing Aerosol OT as an emulsifier. It was found that only CH3Si(NCO)3 among the (CH3)nSi(NCO)4 - n＇s was effective to contribute additional stability for the emulsion without a carbon functional triisocyanate. It was also found that a reaction product of CH3Si(NCO)3 with water reacted with a carbon functional triisocyanate.