A novel method was used to estimate natural mortality (M) of Kuwaiti Penaeus semisulcatus using tagging data. The new M estimator is based on two tagging experiments with similar products of initial survival after tagging times reporting rate, but with different total mortality (Z) values. The best M-estimate for males was 2.4 year -1; the data on the female were, however, inadequate for use by this method. The new method is likely to produce reasonable estimates of M if accurate Z-values are used.