In this article, we solve the duplication problem,where fP n g n!0 belongs to a wide class of polynomials, including the classical orthogonal polynomials (Hermite, Laguerre, Jacobi) as well as the classical discrete orthogonal polynomials (Charlier, Meixner, Krawtchouk) for the specific case a ¼ À1. We give closed-form expressions as well as recurrence relations satisfied by the duplication coefficients.