In this study, the optimum design of reinforced concrete (RC) continuous beams was investigated for different values of live (L) and dead (D) load ratio. The design methodology considers the total material cost of the continuous beam as the objective function. A random search technique was employed. The methodology considers the different cases of live loading and the most unfavorable solution is taken into account. In that case, the amount of the live load is effective on the optimum design. As the numerical example, a two span continuous beam was investigated. During the investigation, the total amount of distributed loads is the same for the cases, but the ratio of L/D is different. According to the results, L/D ratio is effective on the optimum design.