In this report the strength of are carriers and ore/oil carriers is examined in order to establish their design basis. At first the method of calculation is established. The calculation is divided into two steps. First step is the calculation of stresses in case the relative displacement of longitudinal members are neglected. The second step is the calculation of stresses due to the relative displacement of longitudinal members. The stresses calculated by such method were found to coincide with experimental results fairly well. Then the standard load conditions for both are and oil services are adopted among several typical conditions. Analysis of the transverse strength of the are carriers and ore/oil carriers built so far was carried out under the said standard conditions. Finally, considering the results of the calculation and also taking account of the specification of classification societies' rules, design stresses corresponding to such standard condition is determined.