Steam distillation investigations were made on crude oils in porous media to measure steam distillation yields and to determine the effect of process parameters on the distillation mechanism. Experiments were performed in a vertically oriented, 3-ft long, 3-in. diameter cell, designed to avoid steam displacement and entrainment of oil during steam distillation. Both saturated and superheated steam distillations were made on crude oils ranging in gravity from 9/sup 0/ to 36/sup 0/ API. These tests were performed at pressure ranging from 200 to 500 psig and steam temperatures ranging from 387/sup 0/ to 600/sup 0/F. Experimental results show that the equilibrium-saturated steam distillation yields are mainly dependent on the oil composition and may not correlate with crude API gravity. The yields are basically independent of the porous media and steam injection rates investigated. Changes in steam saturation pressure and temperature have insignificant effect on the yields; however, superheated steam significantly increases the yields for some crude oils. (13 refs.)