The paper describes a new method for assessing disclosure risk for tables of counts; the subtraction - attribution probability (SAP) method. The SAP score is the probability of an intruder recovering a .risky. subpopulation table given a quantity of information about the individuals in a population table. The method can be applied to exact or perturbed individual tables and sets of tables. The method can also be used to compare the risk impact of different disclosure control regimes.