The Risk-Rescue Rating is a descriptive and quantitative method of assessing the lethality of suicide attempts. Its underlying hypothesis is that the lethality of implementation, defined as the probability of inflicting irreversible damage, may be expressed as a ratio of factors influencing risk and rescue. Five risk and five rescue factors have been operationally defined, weighted, and scored. Illustrations of typical high risk/high rescue, high risk/low rescue, low risk/high rescue, and low risk/low rescue are presented, together with scoring instructions and tables of values. Risk-rescue ratings correlate well with the level of treatment recommended (none, emergency ward only, hospital admission, and intensive care), with the subject's sex, and whether the subjects lived or died. There is less decisive correlation with age and little correlation with marital status and multiple attempts. Taken by itself, the risk-rescue rating is not a predictive instrument. However, when considered along with other kinds of lethality, such as that of intentionality and psychosocial involvement, the lethality of implementation can add to the basis of individualized suicide prognosis.