To convert the specific conductance C(S,t,p) measured by an in situ CTD sensor to salinity in a manner consistent with the international standard expression proposed by Cox et al., it is necessary to have established a means of estimating the specific conductance of seawater having a salinity of 35‰, [i.e., C(35,t,0)]. Third-order polynomial expressions formulated from samples having salinities near 35‰ are discussed. From the results of this study, it is recommended that an international expression for C(35,t,0) be established and that the conductivity ratio Rt calculated from this standard expression be used to obtain salinity using the UNESCO tables or the equation of Cox et al. Abstract To convert the specific conductance C(S,t,p) measured by an in situ CTD sensor to salinity in a manner consistent with the international standard expression proposed by Cox et al., it is necessary to have established a means of estimating the specific conductance of seawater having a salinity of 35‰, [i.e., C(35,t,0)]. Third-order polynomial expressions formulated from samples having salinities near 35‰ are discussed. From the results of this study, it is recommended that an international expression for C(35,t,0) be established and that the conductivity ratio Rt calculated from this standard expression be used to obtain salinity using the UNESCO tables or the equation of Cox et al.