To date there does not exist one a generally acceptable measure or index of Specialization in International Trade. Development Economic Theory embraces the expectation of a direct relationship between economic growth and export diversification. However, International Trade Theory supports the association of export expansion with increased specialization. The paper proposes a Specialization Index and applies it to six small developing countries: Singapore, South Korea, Malaysia, Mexico, Tunisia and Morocco, during the years of their take offs. Additionally, the index is applied to the two large fast growing economies of Chine and India.