The adsolubilization of styrene, isoprene, and mixtures of styrene and isoprene into cetyltrimethylammonium bromide (CTAB) bilayers (admicelles) on precipitated silica is investigated. The results show that the styrene adsolubilization constant is nearly unchanged with increasing styrene equilibrium concentration in the aqueous phase, while the isoprene adsolubilization constant increases with increasing isoprene partial pressure. The adsolubilization constants suggest that styrene adsolubilizes into both the palisade layer and the core of the admicelle, while isoprene adsolubilizes into the palisade layer. In the co-monomer system styrene adsolubilization is slightly increased in the presence of isoprene but isoprene adsolubilization is significantly enhanced in the presence of styrene; however, the adsolubilization isotherms of both monomers have increasing slopes in the co-monomer system and show that there is a synergistic effect, possibly due to swelling of the admicelle due to the addition of adsolubilizate.