This paper presents the results of model tests performed in the towing tank to investigate the effect of afterbody shapes and also highly skewed propellers on propulsion and propeller excited vibratory forces. The variations of the afterbody shapes were investigated for three model series based on a shallow draft C_b =0.7 gas carrier. One of the three is the parent model, which has a conventional single screw mariner stern. The other two models have a U-shaped stern form with somewhat different degrees of U-shape. The wake measurements have shown that a remarkable reduction of the non-uniformity of wake was attained by both U-shaped sterns. The highly skewed propellers also showed remarkable effectiveness in reducing the propeller excited vibratory forces. Both the highly skewed propellers and U-shaped sterns applied to this type of ship gave no appreciable effect on propulsive performance.