The properties of jojoba oil make it uniquely suited as a raw material for the cosmetics industry. Water-based, thermodynamically stable preparations of jojoba oil are essential in many formulations. New microemulsions were prepared based on jojoba oil and different nonionic surfactants, namely polyoxyethylene-(ethylene oxide) 10 -oleyl alcohol (Brij 96V) and ethoxylated sorbitan esters (Tweens). The effects of the surfactants and of primary alcohols as cosurfactants on the isotropic regions of the phase diagram were elucidated. It was found that, up to a certain cosurfactant chain length, the isotropic region expanded considerably as chain length increased. The size of the isotropic region also increased as a function of the ethylene glycol content of the aqueous phase in microemulsions based on ethoxylated alcohol but shrank when ethylene glycol was included in microemulsions prepared with ethoxylated sorbitan esters. Secondary structural phase transitions from water-in-oil to bicontinuous and to oil-in-water structures (as determined by measuring conductivity and viscosity) were found to be related to jojoba oil content. Dynamic light scattering and small angle X-ray scattering studies established that incorporation of jojoba oil into Brij 96V micelles caused micellar transformation from elongated to spherical droplets and a decrease in the aggregation number.Jojoba liquid wax (also called jojoba oil) is a stable, highly lipophilic, non-toxic "oily" material obtained from the seeds of the desert plant jojoba (Simmondsia chinensis) (Fig. 1). This unique oil differs from common vegetable oils and animal fats in that it is composed mainly (97%) of linear long-chain esters, which are characteristic components of waxes. More than 80% of these are esters of C 18 -, C 20 -, C 22 -, and C 24 -chain monounsaturated alcohols and acids (1).Jojoba wax resists oxidation even at elevated temperatures and can remain chemically unchanged for years. Owing to its excellent ability to penetrate the skin and high resistance to oxidation, jojoba wax is widely used as a component in cosmetics. Its derivatives have potential applications in a variety of commercial fields, including pharmaceuticals and lubrication (1). Numerous recent studies have demonstrated the feasibility of incorporating jojoba as an oil phase in formulas containing active compounds to enhance the efficacy of topical drugs (2,3).The growing interest in microemulsions (ME) for cosmetic and pharmaceutical applications is linked to their physicochemical properties-thermodynamic stability, spontaneous formation, clear appearance, low viscosity, and high solubilization capacity (4). A particularly attractive possibility is that of using ME to enhance the efficacy of molecularly solubilized, hydrophobic, biologically active compounds by providing a readily controlled, stable medium for the solubilized components, together, perhaps, with protection against degradative reactions (5).The use of alcohols as cosurfactants in the preparation of ME has a long history. Alcoho...