This paper shows the interrelationships between measures of inequality and measures of concentration when applied to the measurement of industrial concentration. Gini’s ratio of concentration isthe reference measure which can be applied both to measure the inequality among firms and — in transformation — to measure concentration in the market. The derivation of Gini’s ratio of concentration is presented for the discontinuous case with ungrouped data from the Lorenz curve and from the relative mean difference with repetition. Next, Gini’s ratio of concentration is transformed into a measure of concentration via a conversion formula. Finally, the proposed measurement of industrial concentration is applied to the automobile industries of selected countries.