Transfer of H3-cerebroside sulfate (CS) from aqueous phase to nonaqueous phases (heptane interface) was studied in the absence and presence of opiates, cations and phosphatidylserine. The degree of H3-CS re-distribution was dependent on the concentration of these substances used. The concentration of an opiate agonist (GPA-1657) required to increase H3-CS by 50% in the nonaqueous phase was much lower than that of its corresponding antagonist (GPA-2163) and the value for calcium was 100 times less than sodium. Opiate antagonist (GPA-2163) and phosphatidylserine inhibited the agonist induced re-distribution of H3-CS. Thus, the data seem to indicate that the distribution of H3-CS between these two phases was determined by hydrophobic-hydropholic balance of H3-CS and this balance was dependent on the counter ion pairing with CS. This finding is consistent with our previous observation that opiate agonist-CS complex was more hydrophobic than free CS of the CS-complex formed with opiate antagonist.